|Publication number||CA2600526 A1|
|Application number||CA 2600526|
|Publication date||21 Sep 2006|
|Filing date||10 Mar 2006|
|Priority date||10 Mar 2005|
|Also published as||CA2600529A1, CA2600529C, CN101194129A, CN101194129B, CN101208563A, CN101208563B, EP1856453A2, EP1856453A4, EP1856453B1, EP1856454A2, EP1856454A4, EP1856454B1, US8147302, US20060234621, US20070082601, WO2006099125A2, WO2006099125A3, WO2006099337A2, WO2006099337A3|
|Publication number||CA 2600526, CA 2600526 A1, CA 2600526A1, CA-A1-2600526, CA2600526 A1, CA2600526A1, PCT/2006/8575, PCT/US/2006/008575, PCT/US/2006/08575, PCT/US/6/008575, PCT/US/6/08575, PCT/US2006/008575, PCT/US2006/08575, PCT/US2006008575, PCT/US200608575, PCT/US6/008575, PCT/US6/08575, PCT/US6008575, PCT/US608575|
|Inventors||Eric M. Desrochers, Gordon P. Sharp|
|Applicant||Aircuity, Inc., Eric M. Desrochers, Gordon P. Sharp|
|Export Citation||BiBTeX, EndNote, RefMan|
|Referenced by (1), Classifications (22), Legal Events (2)|
|External Links: CIPO, Espacenet|
DYNAMIC CONTROL OF DILUTION
VENTILATION IN ONE-PASS, CRITICAL ENVIl2ONMENTS
2 This is a continuation-in-part of U.S. Provisional Patent Application Serial No 3 60/660,245 filed on March 10, 2005.
This invention relates to systems for controlling ventilation to dilute contaminants 6 within critical environments or spaces such as laboratories and vivariums which utilize a 7 "one-pass" ventilation strategy in which the airflow out of each environment is entirely 8 exhausted without a recirculated air component, and more particularly, to systems and 9 methods for varying the flows of supply and exhaust air into and from these environments for io the purposes of controlling the dilution of air contaminants based on changes in the presence 11 of these containinants as sensed by a facility monitoring system.
13 This invention relates to the dynamic control of dilution ventilation in one-pass, 14 critical environments. Critical environments in the context of this invention relate to spaces, areas or rooms in which potentially hazardous materials may be used that could become i6 airborne and impact in some way the health of individuals operating within the space.
17 Examples of such spaces include but are not limited to laboratories where chemicals or i8 biological materials are used as well as vivariums or animal research facilities where animals ig are housed for research purposes. Other types of applicable areas include but are not limited to: clean rooms, pharmaceutical processing areas, bio-safety facilities, and medical 21 containment and isolation facilities. Furthermore, critical environments may be further 22 narrowed down to those which are strictly one-pass environments, which in the context of 23 this invention refers to those spaces which use one-pass air, in other words no air from the 24 space is returned or recirculated to an air handler or fan system for use again within the building. As such all air introduced to within the space either from a supply system, or as 26 transfer air from another space, is exhausted typically through some sort of exhaust system 27 which takes the room air and exhausts it from the building typically controlled by some sort 28 of room exhaust or special exhaust air flow control device. Specifically, these rooms have no 29 return air grills or return airflow control devices. Control of the room's airflow is thus accomplished through one or more exhaust airflow control devices designated for the space 31 plus one or more supply airflow control devices that although typically are designated for the 32 space, may also be somewhat remote from the room if some of the air from those devices 1 enters the space as transfer air from another space that is provided with supply airflow via a 2 separate air flow control device. Furthermore, a flow of air that is drawn from or supplied to a 3 space or environment may be expressed as a volume of air per unit time, for example, in 4 terms of cubic feet per minute (cfin).
Dilution ventilation as used in the context of this invention refers to the use of airflow 6 supplied to the room either directly or as transfer air that dilutes or reduces the concentration 7 of possible contaminants in the air of the room. Although capture and containment of 8 hazardous vapors is the safest approach to handling hazardous materials, dilution ventilation 9 provides an important backup or secondary form of protection for the critical environment in lo case the primary or containment control device malfunctions, or else an accident or spill 11 occurs, or the occupants of the space use unsafe practices that introduce contaminants into the 12 air of the room. Dilution ventilation is also sometimes referred to or defined as the minimum 13 level of airflow allowed in the room, or as the airflow corresponding to the critical 14 environment's minimum air change requirement typically expressed as a minimum air changes per hour (ACH) for the space.
16 As the price of oil, natural gas and other fuel sources has increased over the years, 17 there has been interest in reducing the amount of outside air that is used by buildings to save 18 energy, while still maintaining good indoor environmental quality within those facilities. In 1g the context of this invention outside air is defined as the ambient air outside of the building housing the critical environment that maybe drawn into the building to provide some measure 21 of fresh air ventilation. Since laboratory and vivarium facilities typically use 100% outside 22 air these facilities use extremely large amounts of energy compared to other types of facilities 23 such as office buildings that are able to use return or recirculated air.
The purpose of the 24 present invention is to significantly reduce the energy consumption of a critical environment utilizing one-pass or 100% exhaust air for dilution and potentially other purposes while also 26 enhancing the safety of these environments.
27 As mentioned earlier, one example of a critical environment in which a one-pass, 28 dilution ventilation system may be employed is a laboratory. A laboratory generally is a 29 facility that is designed to permit the safe use of various chemicals, biologicals, toxic compounds and/or other potentially harmful substances for research or other purposes. The 31 laboratory may be equipped with one or more "special exhaust devices" that are designed to 32 exhaust air from the lab to an outside environment to protect lab users from potentially 33 dangerous exposure to harmful substances. For example, a laboratory may include one or 34 more of the following special exhaust devices such as laboratory fume hoods, canopy hoods, i glove boxes, or non-recirculating biological safety cabinets, in which potentially harmful 2 substances may be regularly handled. Additionally, exhaust trunks sometimes referred to as 3 snorlcel exhausts are special exhaust devices that may be used to exhaust air containing 4 potentially harmful substances from a particular area on a bench top or from an analytical instrument thereby providing local containment and protection. Additionally, a laboratory 6 may include one or more exhausted storage cabinets that are special exhaust devices that are 7 used to store potentially hazardous substances and function to contain harmful fumes or 8 vapors that might leak from the stored substances. The described laboratory environment may 9 be used for many purposes, such as research, teaching, manufacturing or production, quality control, pilot or scale up, or other functions. Additionally the laboratory may contain many 1i types of areas adjacent to or beyond the research areas such as support rooms, equipment 12 rooms, corridors, offices and other types of rooms found in a laboratory building that may 13 also be one-pass environments with all the air from the spaces exhausted to outside the 14 facility.
Another example of a critical environment in which a one-pass dilution ventilation 16 system may be employed is a vivarium as mentioned earlier. A vivarium is generally'a 17 facility used to house animals for research purposes. These animals which can include rats, i8 mice, rabbits, larger mammals, and even aquatic life such as fish have many environmental 1g requirements. In addition to proper temperature control and lighting, it is important to use containment and or dilution ventilation to reduce and exhaust odors, animal dander, particles, 21 gases from the animal's metabolic functions, and potentially toxic gases from the animal 22 holding and other rooms that are part of these facilities. In addition to protecting the animals, 23 the reduction and elimination of these contaminants in the air is important to the health and 24 safety of the animal care and research staff who use these facilities. In particular, the exposure of these people to animal allergens, such as rat urine protein (RUP) or mice urine 26 protein (MUP), that is often carried in the air on particulates can over time sensitize the 27 animal care workers and researchers, and create allergic reactions in these individuals from 28 the animals via contaminated air in the facility. The vivarium may also have special exhaust 29 devices, for example the animal cage racks that are often used to house rats and mice for example have cages with filter membrane tops and are also ventilated. In particular, these 31 racks may be directly exhausted into a general exhaust duct via a constant, 2-state, or variable 32 air volume valve or other flow control device like a damper-based system.
33 Additionally, some vivarium or animal facility rooms may contain biosafety cabinets 34 that may be exhausted, snorkel exhausts or laboratory fume hoods. Vivariums may also have 1 many different functions similar to the lab room functions mentioned above and similarly as 2 mentioned above may have many types of rooms such as support rooms, surgery, 3 examination rooms, cage wash area, corridors, "clean" corridors, "dirty"
corridors, offices, 4 and other rooms that are part of the animal or vivarium facility that do not house animals yet still are one-pass environments.
6 In view of the foregoing, conventional ventilation processes in a laboratory facility, 7 vivarium, or potentially other similar or related critical environments where dilution 8 ventilation is employed, generally involve supplying 100% fresh outdoor air to the 9 environment in the form of supply air ducted directly into the space or supply air that is 1o supplied to other nearby spaces and then passes into the environment as transfer air or as a 11 constant source of offset air. It should be obvious to those who are experienced with building 12 ventilation system technology that this ducted supply air is usually provided via an air 13 handler that contains a fan to move the air, but also will usually include a method for heating, 14 cooling, and filtering the air. Offset airflow is specifically defined as a typically fixed difference in airflow between the ducted supply into the space and the ducted exhausted 16 airflow from the space. Depending on whether the supply is greater than or less than the total 17 exhaust airflow from the space determines whether the environment is at a positive or 18 negative pressure respectively with respect to an adjacent room or corridor. As an example 1g for labs, typically the supply air is controlled to be less than the exhaust to ensure that the lab is at a negative pressure with respect to the corridor. In the context of this invention, corridor 21 is defined as a passageway that may be adjacent to and is in communication with a plurality 22 of rooms or critical environments.
23 There are three factors that may be typically used to determine the level of supply and 24 exhaust airflow into the critical environment. The first of these factors is the space thermal load. Typically the supply air into the space is conditioned at a temperature such as 55 26 degrees F and used for cooling the environment. The heat sources with in the lab can be solar 27 load, lights, people and the so-called plug loads from the heat generated by equipment and 28 instrumentation within the lab. As these loads increase the cool supply air must be increased 29 to maintain a given temperature set point such as 72 degrees Fahrenheit.
Occasionally, the lab may be cooled using methods other than the supply air such as from a cooled ceiling or 31 floor or from a local fan coil unit that pulls air from the room, passing this air through cooling 32 coils (typically chilled water coils), and passes it back into the room. In these latter two cases 33 the control of the environment's supply and exhaust airflow would be unaffected by the 34 thermal load factor. For purposes of this invention a single pass environment would not be 1 altered from a pressurization standpoint by adding the aforementioned fan coil and, therefore, 2 would be viewed as being a single pass environment even though it may be connected to a 3 locally recirculating fan coil or other device such as a ductless fuine hood, glove box, or other 4 device that locally recirculates air from said environment while having no net influence on the offset airflow to the environment.
6 A second factor that can determine the environment's required supply and exhaust 7 airflow is the exhaust airflow from any special exhaust devices as described earlier as well as 8 the associated make up air needed to match the exhausted airflow. These sources of exhaust 9 air may be fixed sources such as from storage cabinets or biosafety cabinets, two-state lo (high/low) sources or air or fully variable sources such as with variable air volume laboratory 11 fume hoods. Alternatively, the space or environment may have no special exhaust devices 12 and thus this factor will not affect the airflows of the space.
13 The third and final factor affecting the environment's required supply and exhaust 14 airflow is the airflow requirements for dilution ventilation. This requirement is typically expressed as a certain number of air changes per hour (ACH) for the space such as 6 air 16 changes per hour of total exhaust (including special exhaust airflow) or total supply 17 (including offset and transfer) airflow. This number of air changes per hour can then be 18 converted into a specific airflow rate for a given volume space. For example if an 19 environment is 20 feet long by 25 feet wide and 9 feet high, the total volume of the space is 2o 4500 cubic feet. Thus 6 air changes an hour would mean that in 60 minutes the entire volume 21 of 4500 cubic feet would be exchanged 6 times, or equivalently there would be one air 22 change in 10 minutes (60 minutes/6 ACH = 10 minutes per air change). For the volume of 23 4500 cubic feet to be exchanged in 10 minutes would require a total room supply or exhaust 24 flow of 450 cfm (4500 cubic feet/ 10 minutes per air change = 450 cfm).
Typical industry accepted required flows for dilution ventilation range from 6 to 12 air changes per hour.
26 Furthermore, this amount of air changes per hour of airflow is typically a fixed level 27 that is set irrespective of the actual quality of the room air, even though the air exhausted 28 from the lab environment often is clean and safe. Additionally, due to simplicity and costs, 29 some portions of the lab or vivarium environment served by the ventilation system, such as storage areas and support areas, or even offices where there may be no hoods, animals, or 3:L active research are also ventilated with one-pass air at these levels, even though the 32 possibility of contaminants being present in these areas is less likely.
Accordingly, the 33 minimum fixed air changes requirements for 100% outside air in conventional laboratory, 34 vivarium, or other dilution ventilation systems often results in wasted resources (i.e., fresh i outdoor air) and unnecessarily excessive operating costs as well as high up front capital costs 2 for sufficient sizing of the building's heating, ventilating and air conditioning system also 3 referred to as the HVAC system.
4 The typical approach used to integrate the three factors, or requirements mentioned above, into a single flow requirement for total exhaust or supply is simply to take the highest 6 of the three requirements. If constant volume airflow devices are used then they must be set 7 for the highest of the peak requirements of each the three factors. If variable volume airflow 8 control devices are used, then the environment airflow can vary based on the highest of the 9 actual requirements such as the variation in thermal load. Traditionally, in many one-pass, lo critical environments, the dominant factor that has been the controlling factor has been either 11 the thermal load or the requirements of the special exhaust devices such as laboratory fume 12 hoods.
13 As such there have been many inventions and technologies developed to safely vary 14 the environment's airflow to save energy based on either or both of varying airflow to meet the actual thermal load requirements, or varying the airflow through the special exhaust 16 devices. The latter has often been done through the use of variable air volume laboratory 17 fume hoods; such as those described in U.S. Patents Nos. 4,706,553;
4,893,551 and 18 5,240,455; since fume hoods have often been the dominant driver behind laboratory airflows.
19 More complex airflow controls involving the sensing of air contaminants in critical environments that would typically be dominated by thermal loads have also been developed 21 to safely vary and recirculate air from critical environments, such as described in U.S. Patents 22 Nos. 6,609,967 and 6,790,136 through the addition of a return airflow control device to each 23 critical environment to return and reuse clean air in an air handler serving multiple lab rooms.
24 In the last five to ten years, there have two important trends that have affected the airflow levels in labs. First, the numbers of laboratory fume hoods and related special exhaust 26 devices has decreased. This is partly related to the increased use of computers to model 27 chemical reactions vs. lab experimentation, as well as the use of smaller amounts of 28 chemicals in research. Additionally, more life sciences labs that tend to have less fume hoods 29 are being built today vs. the traditional chemistry lab with many fume hoods. Furthermore, many labs today are built with variable air volume laboratory fume hood control systems to 31 reduce the amount of exhaust and make up air related to the fume hood. As a result the lab 32 ventilation requirements related to special exliaust or fume hood make up air have been 33 reduced significantly, so that in many labs it is not the driving force determining the airflow 34 or ventilation in the lab.
1 Second, thermal loads in labs have also dropped as more energy efficient technologies 2 are being used in labs. The efficiency and waste heat from lighting for example has dropped 3 significantly as has the power used by lab instrumentation. Although in the early 90's the 4 amount of lab instrumentation increased significantly, over time this equipment has become smaller and more energy efficient. Refrigerators and freezers have in many cases dropped 6 their power consumption by two-thirds, plus LCD displays and laptops have replaced desktop 7 computers and large energy hungry CRT monitors. Many recent studies show this result, 8 such as a study from the Lawrence Berkeley National Laboratory mentioned in the 9 September, 2005 issue of HPAC Engineering entitled "Right-sizing Laboratory HVAC
1o systems". This article demonstrates that labs are often over designed for thermal loads that 11 are 5 to 10 times more than what the lab environment will actually be used for.
12 As a result of these two trends, the minimum or dilution ventilation requirement has 1.3 emerged as often the dominant and controlling factor in laboratory airflow requirements. If 14 this level can, on average, be reduced it would save significant amounts of energy in laboratories as well as allowing a smaller HVAC system that would save first cost in the 16 construction of the facility. As a point of fact, the level of minimum air change or dilution 17 ventilation requirements are also usually set somewhat arbitrarily, for example at levels of i8 between 6 to 12 air changes per hour for a laboratory or 10 to 20 ACH's for a vivarium.
19 Occasionally to save energy, this dilution rate is made a two state flow reduced during unoccupied times to a set lower level such as 4 ACH and then increased during occupied 21 times to a higher level such as 8 ACH. This control can occur by a set time schedule control 22 or through the use of an occupancy sensor such as those commonly used to shut off lights.
23 Although this approach can save energy it has several safety problems that negate its prudent 24 use. For example, a spill or release of hazardous vapors can occur during an unoccupied time increasing the level of contaminants in the air above safe levels. If someone were to walk into 26 the space during this scheduled unoccupied time, they could be injured by the higher level of 27 contaminants in the air. Even with an occupancy sensor or detector, when the individual 28 walked into the room the level of contaminants could be quite high, exposing the individual 29 until the system both detected their presence and more importantly was able to adequately flush out the lab with the higher occupied airflow which could take some time.
Furthermore, 31 occupancy detectors can have problems with detecting people in a broken up space with 32 many barriers such as lab shelves and equipment between the sensor and the occupants. They 33 also need to constantly see motion to operate and may fail to see someone quietly reading 34 with insufficient motion to trigger the higher safe airflow. If the flow is dropped due to lack 1 of sufficient motion, the occupant might not notice the flow change and then even worse 2 could possibly be overcome by a higher level of contaminants in the lab.
4 It is therefore a primary object of this invention to provide a system for controlling ventilation to dilute contaminants within critical environments or spaces, such as laboratories 6 and vivariums which utilize a "one-pass" ventilation strategy in which the airflow out of each 7 environment is entirely exhausted without a recirculated air component.
8 It is a further object of the invention to provide systems and methods for varying the 9 flows of supply and exhaust air into and from these environments for the purposes of controlling the dilution of air contaminants based on changes in the presence of these 11 contaminants as sensed by a facility monitoring system.
12 The systems and methods of the invention were developed using a novel, improved 13 approach, from both a safety and an energy.savings perspective over the prior art use of a 14 time clock or occupancy sensor, to vary minimum ventilation levels would be to instead vary the amount of dilution ventilation airflow or equivalently defined in the context of this 16 invention, the air change rate of a space, based on the level of an air contaminant in the space 17 as measured by a facility monitoring system. In the context of this invention a facility 18 monitoring system is defined as a monitoring system that includes at least one air 19 contaminant sensor that measures at least one air contaminant of at least one room, space, 2o area or critical environment. Such a facility monitoring system may involve the use of one or 21 more individual, local, wired or wireless sensors located in the space being measured. It may 22 also use remote or centralized air contaminant sensors that are multiplexed or shared amongst 23 a plurality of spaces as is described in more detail later. Finally, a facility monitoring system 24 may use a combination of the previously nlentioned remote and local air contaminant sensors.
As such these facility-monitoring systems may be used to measure many different air 26 contaminants as well as potentially other characteristics of the monitored space such as 27 temperature, humidity, or differential pressure with respect to some other space.
28 An air contaminant sensor in the context of this invention refers to a sensor that 29 converts the level of or information about the presence of an air contaminant into either a 3o continuously varying or else discontinuous pneumatic, electronic, analog or digital signal or 31 else into a software or firmware variable representing the level of or information about the 32 presence of an air contaminant in a given space. The air contaminant sensor may be based on 33 any of a variety of sensing technologies known to those skilled in the art such as for example 34 electrochemical, photonic or optical, infrared absorption, photo-acoustic, polymer, variable 1 conductivity, flame ionization, photo-ionization, solid state, mixed metal oxide, ion mobility, 2 surface acoustic wave, or fiber optic. The air contaminant sensor may be a wired or wireless 3 sensor type and be implemented with various types of physical hardware such as for example 4 micro-electro-mechanical system based (MEMS), nanotechnology based, micro-system based, analog based, or digital based, Additionally, an air contaminant sensor may sense for 6 more than one air contaminant, may include more than one air contaminant sensor in one 7 packaged device, or may sense for or include sensors for other non-contaminant air 8 parameters such as for example temperature, pressure, or a measure of humidity. In the 9 context of this invention, air contaminants refers to certain chemical, biological, or 1o radiological composition elements or properties of the air such as for example carbon ii monoxide (CO), particles of various sizes, smoke, aerosols, TVOC's (Total Volatile Organic 12 Compounds), specific VOC's of interest, formaldehyde, NO, NOX, SOX, S02, nitrous oxide, 13 methane, hydrocarbons, ammonia, refrigerant gases, radon, ozone, radiation, biological and 14 or chemical terrorist agents, mold, other biologicals, and other chemical characteristics of the air and contaminants of interest to be sensed. Also, in the context of this invention the term 16 air contaminants specifically does not include or refer to such air characteristics or 17 paraineters such as any measure of temperature, carbon dioxide, or humidity such as for 18 example any of the linked measures of temperature and moisture or water vapor in the such 1g as relative humidity, absolute humidity, wet bulb temperature, dry bulb temperature, dew point temperature, or grains of moisture per pound of air. Additionally, in the context of this 21 invention, air contaminants also does not specifically include or refer to any measure of 22 airflow volume, velocity or pressure such as air volume as may be indicated in units of cubic 23 feet per minute of air or other units, velocity pressure, air speed or velocity, static pressure, 24 differential pressure, or absolute pressure.
The air in modern laboratories is often quite clean such that high air change rates are 26 unnecessary except for example when a spill happens; poor lab practices generate fumes, 27 vapors or contaminants in the lab outside the containment devices like fume hoods; or when 28 the containment devices work poorly leaking chemical fumes into the space.
Since the far 29 majority of the time the lab air is clean, the dilution ventilation airflow can be brought down significantly the majority of the time to a level such as 2 to 4 ACH's vs 6 to 12 ACH's 31 creating significant ventilation savings. Additionally when a spill occurs, the system can 32 increase the dilution ventilation rate to a high level such as 12 to 15 ACH, providing 33 increased safety through a fast evacuation of the spilled vapors from the lab.
1 Dynamic control of dilution ventilation based on monitoring the quality of air with a 2 facility monitoring system can be accomplished with several different embodiments. Perhaps 3 the simplest approach to dynamically vary air change requirements in one-pass, critical 4 environments, such as labs or vivariums, would be to use a single, broad based contaminant sensor such as a TVOC or total volatile organic compound sensor located in each room or 6 airflow control zone that is to be controlled. This approach can for example increase the 7 dilution ventilation airflow requirements when the contaminant sensor detects that 8 contaminants are above a given threshold level. When the contaminant level returns below 9 the given threshold level, the dilution ventilation airflow requirement is brought back down to io the minimum set point level. In all conditions if the thermal load or special exhaust make-up 11 airflow requirements are above the required dilution ventilation flow requirements, then these 12 requirements will override and take control of the room's airflow level in a high select form 13 of control.
14 There are several important issues to be taken into account when implementing this type of one sensor per room/airflow control zone approach to the dynamic control of dilution 16 ventilation. First of all, the selection and use of lower cost, typically metal oxide type TVOC
17 sensors may create problems due to the relatively high drift and even poisoning and 18 degradation that can often occur with these types of sensors when they are exposed to certain 19 airborne contaminants that are likely to be found in labs, vivariums or other environments where outside air is used to dilute airborne contaminants. A preferred alternative would be to 21 use a higher-grade TVOC sensor such as for example a photo-ionization detector (PID) style 22 sensor. These sensors although typically more expensive, are also more stable and much less 23 apt to be compromised by the gases they are detecting.
24 Additionally, the use of a TVOC sensor, even a PID type TVOC sensor, will not detect all contaminants of concern in a lab. For example, there could be a release of an 26 aerosol, hazardous particles, or smoke from an out of control reaction that needs to be rapidly 27 evacuated from a lab. Similarly, non-organic acid gases, for example, could be quite harmful 28 to a researcher but similarly will not be detected by a TVOC sensor.
Furthermore, there may 29 be certain specific contaminants that are of concern that would be beneficial to sense such as formaldehyde or ammonia. Finally, depending on the allowed minimum air change level, if a 31 space may be heavily occupied, such as with a teaching lab, C02 monitoring may be needed 32 as a means of detecting heavy occupancy levels and increasing airflow to meet outside air 33 requirements and guidelines related solely to the amount of people in the space such as to 34 meet a typically used guideline of 15 to 20 cfm of outside air per person.
As such an 1 embodiment that can be used to deal with these issues would use multiple sensors vs. just one 2 sensor in one or more rooms or where it is appropriate to detect some of these other 3 contaminants to provide safe operation of the system and potentially also to sense C02 for 4 additional airflow control related to occupancy.
An exemplary embodiment of the current invention that provides another solution to 6 these issues and is both practical and cost effective is the use of a multipoint air sampling 7 system, otherwise known as a multiplexed or shared sensor based facility monitoring system, 8 as the means to sense the quality and cleanliness of the lab environment.
Multipoint air 9 sampling system are defined for the purposes of this patent as specifically a facility 1o monitoring system that uses shared or multiplexed sensor(s) consisting of either a single 11 remote sensor or a set of remotely located sensors that is used to monitor a plurality of 12 spaces, areas or rooms within a building, or outside adjacent to a facility by transporting 13 samples or packets of air from the critical environment to be monitored to the at least one air 14 contaminant sensor.
For one class of these multipoint air sampling systems specifically defined, in the 16 context of this invention, as star configured multipoint air sampling systems or just star 17 configured systems, multiple tubes may be used to bring air samples from multiple locations 18 to a centralized sensor(s). Centrally located air switches and/or solenoid valves may be used 1g in this approach to sequentially switch the air from these locations through the different tubes to the sensor to measure the air from the multiple remote locations. Each location may be 21 sensed for between 10 seconds or several minutes. Depending on how many locations are 22 sensed each space may be sensed on a periodic basis that could range from 5 to 60 minutes.
23 These star configured systems may be called octopus-like systems or home run systems and 24 may use considerable amounts of tubing. An example of such a star configured system is described in U.S. Patent No. 6,241,950, which is incorporated herein by reference. Other 26 types of known air monitoring systems include those that have been designed to monitor 27 refrigerants and other toxic gases, which also are star configured systems.
Additionally, these 28 types of star configured systems have been used to monitor particulates in multiple areas such 29 as clean room areas with a single particle counter. Generally, these types of systems have not 3o historically been applied to general air quality measurement applications involving multiple 31 parameters such as TVOC's.
32 Another multipoint air sampling system defined in the context of this invention as a 33 networked air sampling system uses a central "backbone" tube with branches extending to 34 various locations forming a bus-configured or tree like approach similar to the configuration 1 of a data network. Air solenoids are typically remotely located proximate to the multiple 2 sampling locations. The sampling time for each location like with the star configured 3 systems may vary from about 10 seconds to as much as several minutes. A
typical sampling 4 time per location would be about 30 seconds, so that with 301ocations sampled, each location could be sampled every 15 minutes. Networked air sampling systems can also include 6 remote and/or multiple-location air sampling through a tube or pipe for sampling locations in 7 a building, outdoor air or ambient sampling, and exhaust air stacks. An exemplary networked 8 air sampling system is described in U.S. Patent No. 6,125,710, which is incorporated herein 9 by reference.
Finally another multiplexed form of facility monitoring system that may be used to 11 implement portions of this invention is defined in the context of this invention as a networked 12 photonic sampling system that multiplexes packets of light vs. packets of air and may 13 incorporate either a star configured or networldbus type of layout. The basic concept uses a 14 central laser emitter and a central laser detector that sends out and detects laser light packets that are switched into rooms to be sensed by optical switches. Optical fiber sensors, infrared 16 absorption cells or sensors, and other sensing techniques are located and used in the sensed 17 area to change the properties of the light due to the affect of the environment. The light 18 packet is then switched back to the central detector where the effect of the environment on 19 the light properties is determined. A major benefit of the system is that the sensors such as the fiber or open cell sensors are potentially quite low in cost. The expensive part is the laser and 21 detector systems that are centralized. Like in the previous multipoint air sampling systems, 22 multiple affects on the light from particles, gases and other contaminants, humidity, etc. can 23 be done simultaneously with central equipment and the telecom concept of Wavelength 24 Division Multiplexing which allows multiple wavelengths and hence multiple signals to share the same fiber. A clear advantage of this system is the ability to have a cycle time that can be 26 in ten's of milliseconds or less. This sampling system is detailed in U.S.
27 6,252,689, entitled "Networked Photonic Distribution System for Sensing Ambient 28 Conditions" which is also incorporated herein by reference.
29 The multipoint air sampling systems and networked photonic sampling system which have been described heretofore and are collectively referred to as sampling systems may be 31 applied to monitor a wide range of locations throughout a building, including any kinds of 32 rooins, hallways, lobbies, interstitial spaces, penthouses, outdoor locations, and any number 33 of locations within ductwork, plenums, and air handlers. To provide control as well as 34 monitoring of these different spaces, virtual sensor signals can be created that in the context 1 of this invention refer to software or firmware variables, or continuous analog or digital 2 signals that can be passed to other systems such as a building control or laboratory airflow 3 control system and are representative of the state of a given space's air contaminant value. In 4 effect these signals are reflective of what a local sensor would read if it was being used instead of the multipoint air sampling system or networked photonic sampling system 6 otherwise known collectively again as sampling systems.
7 Another characteristic of these sampling systems is that some characteristics or 8 parameters of the air such as temperature in particular, as well as some air contaminants such 9 as potentially ozone can not always be effectively measured from a remote location with a 1o shared sensor. Furthermore, other contaminants may be accurately measured at a remote 11 location with a shared sensor but, for various reasons such as the need for more rapid 12 sampling, may be preferably sensed locally at one or more of the sensed locations. In these 13 situations, separate local sensors and either distinct signal wires or a digital data 14 communications network with cable, optical fiber or wireless links can be used to connect these local sensors such as temperature sensors to either the networked air sampling system, 16 star configured multipoint air sampling system, networked photonic sampling system, or 17 possibly a building management system. These virtual sensor signals plus potentially local i8 sensor signals can be combined to create blended signals that may be used advantageously for 19 monitoring and or control purposes as described in U.S. Patent Application entitled, "MULTIPOINT AIR SAMPLING SYSTEM HAVING COMMON SENSORS TO
22 MONITORING AND BUILDING CONTROL" and filed on March 10, 2006, which is 23 incorporated herein by reference.
24 When the multipoint air sampling systems are used to sample ductwork, plenums, air handlers or any other applications where flowing air in a partially contained area such as a 26 duct or pipe is to be sampled and measured with a remote sensor, a tube or hollow duct probe 27 may be inserted into the duct or partially contained space to withdraw a sample or else a hole 28 can be made in the duct and a sample drawn from the duct from a tube connected to the 29 opening in the duct wall. Additionally however, a separate temperature or other parameter or contaminant sensing probe or probes are needed to make whatever local sensor measurements 31 are desired from these ducts or partially enclosed areas. Multiple separate probes for both 32 sensing the flowing air stream and for drawing air samples may be employed or a unique 33 integrated sampling probe that uses one probe for both local air characteristic measurements 34 and for air sampling may be used as described in the U. S. Patent Application Serial No.
1 11/312,164, entitled "DUCT PROBE ASSEMBLY SYSTEM FOR MULTIPOINT AIR
2 SAMPLING" which is incorporated herein by reference.
3 Another embodiment of the current invention uses the virtual signals from a 4 multipoint air sampling system and or the signals from local room or duct air contaminant sensors and combines them via one or more of multiple approaches using a signal processing 6 controller to create a dilution ventilation command signal that in the context of this invention 7 is an airflow command signal that can be used to vary at least partially the dilution ventilation 8 airflow or air change rate of a critical environment based on one or more air contaminants.
9 For the purposes of this patent, an airflow command signal is any pneumatic, electronic, analog or digital signal, or a software of firmware variable that operates in a 11 firmware or software program running on a microprocessor or computer, that is used by 12 either the critical environment airflow controller or by one of the room exhaust, special 13 exhaust or supply airflow control devices to at least partially vary or control one of the 14 aspects of or relationships between any one of the airflows moving into or exiting the critical environment. This airflow command signal may be of a continuously varying nature and is 16 otherwise referred to herein as a VAV or variable air volume command signal. Otherwise, the 17 airflow command signal may be a discontinuous airflow command signal which in the 18 context of this invention is defined as a signal that may have only two levels or states and for ig the purposes of this patent is referred to as a two state signal, or it may have three levels or states and may thus be referred to in the context of this invention as a three state signal.
21 Alternatively, the discontinuous airflow command signal may have multiple discrete levels or 22 states and as thus may be referred to herein as a multiple state signal.
23 When multiple air contaminants are to be used by a signal-processing controller to 24 create a dilution ventilation airflow command signal, particularly where each contaminant has a different threshold of concern, each contaminant can be scaled to a standard scale relative to 26 that threshold. For example 2 volts in a 0 to 10 volt scale can represent the threshold at which 27 point the airflow begins to be increased with 10 volts representing maximum flow. These 28 individual signals can then be high selected so the higher of these signals controls the dilution 29 flow. Alternatively, the signals can be summed together after they have been weighted in a relative manner based on the severity of the health effects of each sensed compound.
31 Another problem of concern with the dynamic control of dilution ventilation based on 32 the measurement of air contaminants in a space is that if outdoor levels of a contaminant go 33 high due to re-entrainment of "dirty" exhaust flows, high outdoor dust levels, traffic, etc, the 34 system could be triggered by these levels and increase the supply airflow into the rooms. This 1 action would actually make matters worse and would "latch" virtually all the controlled 2 spaces up at the high ventilation level. Since the system capacity would have been likely not 3 designed for each space operating at maximum flow then, this event would call for a system 4 capacity that could not be achieved. This potentially could compromise the airflow control throughout the building, reducing flows, and thereby creating loss of capture with the special 6 exhaust devices as well as potentially compromising room pressurization levels. A similar 7 problem of exceeding system capacity could also be achieved if for example the hallways of 8 a lab or vivarium are being mopped with a cleaner that gives off VOC's. The floor cleaner 9 fumes could be quickly pulled into many of the negatively pressurized lab rooms thereby 1o triggering many of the lab spaces into a high flow level state, thereby creating a similar 1i capacity problem.
12 To prevent multiple spaces from going to high dilution ventilation incorrectly due to a 13 high outdoor level of contaminants, another embodiment of the current invention describes a 14 means to vary the dilution ventilation of a space not on the absolute value of a given contaminant, but instead on the differential value of that air contaminant vs.
either an outdoor i6 air value, a supply airflow value, or the value measured in an adjacent or nearby space. In this 17 manner the room does not incorrectly increase the flow of a contaminated supply air stream, 18 when the contaminant sensed is not from inside the room. In a related embodiment, if the 19 absolute level of the room exceeds the threshold value for action, yet the source of the contaminant is from the supply of outside air, the supply air may be decreased. For example, 21 the supply air may be decreased by commanding a lower dilution ventilation level and/or 22 commanding an increased temperature set-point, to reduce the thermal load requirements on 23 the supply volume.
24 For those critical environments where there is a concern that a spill or contamination of the room could spread to other rooms or for other reasons requiring increased containment 26 or protection, a further embodiment of the present invention could increase the exhaust air 27 and decrease the supply air of the affected room or area to increase the negative pressure 28 offset of the contaminated room to increase the level of containment of that space vs. other 29 spaces. If a given room is believed to the source of a potential contamination, then surrounding rooms could be increased to a positive pressure to further isolate the 31 contaminant.
32 For the purposes of this patent a signal processing controller as mentioned above 33 refers to analog or digital electronic circuitry, and or a microprocessor or computer running a 34 software or firmware program that uses at least information, signals and or software or 1 firmware variables from either individual local sensors of air contaminants and or other air 2 characteristics such as temperature, humidity, air volumes, or pressures plus virtual sensor 3 signals, information and or software or firmware variables from remote, centralized sensors 4 of air contaminants, and combines and processes this information in a potential multitude of ways. As a result the signal processing controller either creates airflow command signals for 6 dilution ventilation, offset air volumes, or other airflow commands to be used by a critical 7 environment airflow controller, and or create signals or information that can be used by other 8 control devices such as a building control system for at least partially controlling one or more 9 critical environment airflows of supply, room exhaust, special exhaust or offset airflow, and io or is used for some other control or monitoring function that is in some way related to the 11 control of one of the aforementioned critical environment airflows.
12 In the context of this invention, a building control system or building management 13 system as mentioned above is defined as a control system located in a building or facility that 14 is used to control one or more functions of the HVAC system in a building such as for example control of space temperature, space relative humidity, air handling unit airflows and 16 operation, exhaust fan flows, chiller operation, duct static pressures, building pressurization, 17 critical environment airflows. These systems often integrate with or incorporate other 18 building systems or subsystems such as fire and security, card access, closed circuit TV
lg monitoring, smoke control systems, power monitoring, and critical environment airflow control systems. Building control systems may have pneumatic, electric, electronic, 21 microprocessor, computer, or web based controls using pneumatic, analog and or digital 22 signal inputs and outputs. These systems often have centralized monitoring functions, 23 centralized or local control capabilities, and may have Internet or web based access. They 24 may also be referred to as building management systems (BMS), facility control systems or facility management systems (FMS).
26 Finally, there may be improved or at least alternative approaches to increasing 27 ventilation in a lab that has a spill event. For example is the door of the space to the corridor 28 has been left open, the slight negative pressure of the lab room vs. the corridor may not be 29 enough to prevent the spill vapors from contaminating other adjacent areas.
It may be better to specifically have the system react in some other way to ensure that the vapors are 31 contained in the room with the spill.
2 Other objects, features and advantages will occur to those skilled in the art from the 3 following description of the preferred embodiments and the accompanying drawings in 4 which:
FIG. 1 is a schenlatic diagram of a preferred embodiment of the system of the 6 invention in which a plurality of one-pass, critical environments are being monitored by a 7 multipoint star configured air sampling system.
8 FIG. 2 is a schematic diagram of a preferred embodiment of the system of the 9 invention in which a plurality of one-pass, critical environments are being monitored by a 1o multipoint networked air sampling system.
11 FIG. 3 is a detailed schematic diagram of a preferred embodiment of the system of the 12 invention in a one-pass, critical environment.
13 FIG. 4 is a schematic diagrani of a portion of a preferred embodiment of the signal 14 processing logic of the invention that may be used to create the dilution ventilation command signals.
16 FIG. 5 is a schematic diagram of an embodiment of the critical environment airflow 17 controls logic of the invention for a one-pass, critical environment space including one or 18 more special exhaust sources.
19 FIG. 6 is a schematic diagram of an embodiment of the system of the invention in which a plurality of one-pass, critical environments are being monitored by one or more of 21 individual local sensors comprising one or more unique features.
22 FIG. 7A and 7B are schematic diagrams of various steady-state levels associated with 23 air change rate control sequences.
24 FIGS. 8A and 8B are diagrammed strategies for controlling the air change rate in critical environments using a closed loop system to provide dilution ventilation control by 26 varying the air change rate within a critical environment.
29 FIG. 1, 2 and 6 all show a typical set of monitored critical environments or rooms 3o 20A, 20B, and 20C that have doors entering a corridor 10 that is also being monitored. Due 31 to a positive or negative pressurization of the critical environments, an offset may exist 32 between the critical environment space or area and an adjacent space. An example of this is 33 shown in FIG. 1, 2 and 6 as offset airflow 21A, 21B, and 21 C between the spaces 20A, B, 34 and C and corridor 10. Although the diagrams show three rooms and a corridor, the present invention may be used with any plurality of rooms or spaces including corridors or otller 1 adjacent spaces that are also being monitored, such as for example, two or more critical 2 environments, or one corridor plus one or more spaces. Note also that, although the critical 3 environments shown in the Figures are enclosed within walls, critical environments in the 4 context of this invention may also be a section or area of a room having no walls or partitions around it. Thus, there may be multiple critical environments within one physical room.
6 Alternatively, multiple physical rooms may also constitute one critical environment or space.
7 Typically, the critical environment 20 will also be an area that is fed by one or more supply 8 airflow control devices 51 plus one or more room exhaust devices 41 that are being 9 controlled by a critical environment airflow controller 30 as one airflow control zone. For the purposes of this patent a critical environment airflow controller is an airflow control 11 apparatus that may be of analog or digital electronic design or may be constructed using a 12 microprocessor or computer running a software or firmware program that creates the airflow 13 command signals for one or more supply and or exhaust airflow control devices possibly 14 using information, signals and airflow commands from other devices, systems or controllers.
FIG. 5 shows one embodiment of a critical environment airflow controller.
16 These sets of rooms in FIG. 1, 2 and 6 are further described as having a source of 17 supply air from supply air ducts 50A, 50B, and 50C that may exit the room as room or 18 general exhaust air from room or general exhaust ducts 40 A, 40B, and 40C.
Although not i9 shown in the figures, the corridor 10 often has a source of supply air and possibly room 2o exhaust as well. The supply ducts 50A, B and C also contain airflow control devices 51A, B, 21 and C. which supply air into the room or space through supply flow grill or diffuser 52A, B, 22 and C respectively. Additionally, the room exhaust ducts 40A, B, and C
contain room 23 exhaust airflow control devices 41A, B, and C which control the amount of room or space air 24 pulled into the room exhaust duct through a room exhaust grill or vent opening 42A, B, and C
26 FIG. 1, 2, and 6 also show the presence of an outdoor air intake 62 into the building 27 through outside air duct 60. This duct could be connected to or part of some type of an air 28 handling unit to pull in outside air into the building or may be a special duct or outside air 29 piclcup location specifically used for or shared by the air sampling systems 100 and 200 of 3o FIG. 1 and 2 respectively or the air contaminant sensing system of FIG. 6.
31 An airflow control device as used in the context of this invention, such as the supply 32 and room exhaust airflow control devices 51 and 41 respectively or the special exhaust 33 airflow control device 71 shown in FIG. 3, is defined as any device known to those skilled in 34 the art of airflow control for controlling air flow volume and velocity through a duct. For 1 example, they can be constant volume, two state, multiple state, or variable air volume 2 (VAV) boxes or terminals such as manufactured by Titus, Metal Aire, Enviro-Tec, or others.
3 These devices use a damper or throttling device of some type such as a single round, square, 4 or rectangular blade damper, a multiple blade damper, a set of pneumatic bladders that can be used to seal off an opening, or any other type of throttling device that can be used to seal off a 6 duct, that is connected to a pneumatic, electric, or electronic actuator that is controlled by a 7 pneumatic, electronic, digital, or microprocessor based controller which typically also relies 8 on feedback of flow from a flow sensor for closed loop control of the duct's air volume.
9 These flow sensors can be of various types known to those skilled in the art, such as those 1o based on single or multiple velocity pressure sensors, hot wire, heated thermistor, 11 microelectronic flow sensor, etc. Alternatively, another type of flow control device that is 12 commonly used is an airflow control valve that typically has a venturi shaped body with a 13 spring loaded cone that moves through the venturi shaped throat of the device to provide 14 inherent, pressure independent control of volume, such as manufactured by Phoenix Controls or others. These valves typically have pneumatic, electric, or electronic actuation to provide 16 constant volume, two-state, multiple state, or variable air volume control.
These devices often 17 have large turndown or flow ranges that make them very appropriate for dynamic control of 18 dilution ventilation that can have wide flow ranges to achieve optimum energy savings and 19 safety. Finally, another example of an airflow control device may be some form of a single or multiple blade damper or other type of throttling device that is located either in an air 21 handling unit or a duct serving one or more areas or potentially multiple critical environments 22 which further includes one of the airflow measuring devices aforementioned or similar 23 airflow measuring devices that are adapted using a grid of sensors or sensing holes for 24 example to measure the airflow accurately across a large cross sectional duct area.
Although not shown in FIG. 1, 2, and 6 the critical environments 20A, B, and C
may 26 also have one or more special exhaust airflow devices as mentioned above which also pull air 27 out of the critical environments. An example of this is shown in FIG. 3 as special exhaust 28 device 72, and special exhaust airflow control device 71 which will be both explained in 29 more detail later.
With reference to FIG. 1, this diagram refers to a preferred embodiment of the present 31 invention directed to dynamic control of dilution ventilation in one-pass, critical 32 environments using a star configured multipoint air sampling system 100.
Multipoint air 33 sampling system 100 could be a star configured multipoint air sampling system with a 34 structure lilce that described in U.S. Patent No. 6,241,950; U.S. Patent No. 5,292,280; U.S.
1 Patent No 5,267,897; U.S. Patent No. 5,293,771 or U.S. Patent No. 5,246,668.
It could also 2 be a refrigerant and toxic gas monitor adapted for this purpose such as the Vulcain Inc.
3 multipoint sample draw gas monitor model number VASQN8X as can be seen on their 4 website at www.vulcaininc.com or a multiplexed particle counter such as the Universal Manifold System and Controller made by Lighthouse Worldwide Solutions, Inc., as can be 6 seen at their website at www.golighthouse.com, coupled with one of their particle counters 7 such as their model number Solair 3100 portable laser based particle counter or an 8 obscuration based particle sensor. It could also be a star configured multipoint air sampling 9 system like that of the AlRxpert 7000 Multi-sensor, Multipoint Monitoring system 1o manufactured by AlRxpert Systems of Lexington, Massachusetts, as can be seen at their 11 website at www.airexpert.com.
12 In FIG. 1, a set of solenoid valves 161 through 167 is part of a multipoint air sampling 13 system 100. Equivalently, these solenoids 161 through 167 could be replaced with other 14 switching means such as SSS-48C Single Scanivalve System manufactured by the Scanivalve Corporation of Liberty Lake, Washington as can be seen on their website, 16 www.scanivalve.com, which uses a pneumatic selector switch and stepper motor to connect 17 one of many input ports to an outlet port which can be connected to a sensor such as a 18 pressure sensor. The solenoid valves 161 through 167 are controlled to switch in a sequence 19 by control logic 110. This sequence may be a simple sequential pattern of one solenoid after 2o another, or varied for example through programming to be one of potentially many preset 21 patterns, or it can have a pattern that can be interrupted and changed to a new sequence by 22 inanual or remote command or by a trigger event based on the values or signal pattern of one 23 or multiple sensed contaminants. This trigger event could be generated from outside the 24 multipoint air sampling system 100 or could be created from the sensor information processed by signal processing controller block 130.
26 The solenoid valves 161 through 167 are connected to sampling locations 13, 23A, 27 and 23C in the spaces as well as duct sensing locations 43A, 43B, 53B, and 63 through tubing 28 14, 24A, 44A, 44B, 54B, 24C, and 64. In FIG. 1 for example, sampling location 13 in 29 corridor 10 is connected through tubing 14 to solenoid 161. Area sensing locations 23A and C in rooms 20A and C are connected through tubing 24A and C to solenoids 162 and 166 31 respectively. Room exhaust duct sampling locations 43A and B are connected through tubing 32 44A and B to solenoids 163 and 164 respectively. Supply duct sampling location 53B is 33 connected through tubing 54B to solenoid 165. Finally outside air duct sampling location 63 i is connected through tubing 64 to solenoid 167. Alternatively, tubing 64 may be connected 2 to some other suitable location other than duct 60 to obtain outside air samples.
3 The tubing mentioned above transports the air sample from the sensing location to the 4 solenoid of the multipoint air sampling system 100. The tubing typically will have an inner diameter of one eighth to one half an inch in diameter with a preferred inner diameter of 6 about one quarter inches. This tubing can be made of standard plastic pneumatic tubing such 7 as Dekoron TM low density polyethylene (LDPE) plastic, Teflon, stainless steel, "Bev-A-8 Line XX " tubing made by Thermoplastic Processes, Inc. of Stirling, NJ, or other suitable 9 tubing materials known to those skilled in the art. For superior performance in transporting both TVOC's and particles however, a material that is both inert to VOC's with very little 11 adsorption and desorption as well as electrically conductive to prevent static buildup is 12 preferred such as flexible stainless steel tubing. Other preferred materials and constructions 13 are described in U.S. Patent Application Serial No. 10/948,767, filed on September 23, 2004 14 entitled, "TUBING FOR TRANSPORTING AIR SAMPLES IN AN AIR MONITORING
SYSTEM", as well as U.S. Patent Application Serial No. 11/149,941 filed on June 10, 2005, 16 entitled, "AIR MONITORING SYSTEM HAVING TUBING WITH AN ELECTRICALLY
17 CONDUCTIVE INNER SURFACE FOR TRANSPORTING AIR SAMPLES".
18 Additionally in FIG. 1, a vacuum pump 140 pulls air from the sensing locations 19 through the tubing into the solenoids 161 through 167 and into a manifold 190 connecting all the output ports of the solenoids together and to the inlet of the shared sensors 120. The outlet 21 of the shared sensors 120 is connected to the vacuum pump by tubing 141, whose 22 construction is not critical and can be inexpensive plastic tubing such as the Dekoron TM
23 mentioned above or other. The inner diameter of this tubing can be made similar to the size of 24 the tubing connecting to the inlets of the solenoid valves or possibly larger for less pressure drop. The shared sensors 120 can consist of one or more sensors to measure such air 26 characteristics as humidity, CO2, dewpoint temperature, and differential static pressure., as 27 well as air contaminants such as for exatnple, CO, particles, smoke, TVOC's, specific VOC's 28 of interest, formaldehyde, NO, NOX, SOX, nitrous oxide, ammonia, refrigerant gases, radon, 29 ozone, biological and or chemical terrorist agents, mold, other biologicals, and other air contaminants of interest to be sensed. These sensors may be connected in series, in parallel 31 or a combination of both.
32 The signal outputs of the shared sensors 120 are passed to the signal processing 33 controller block 130 of the multipoint air sampling system 100. This block 130 also accepts 34 other sensor information from the sensor inputs block 150. This input block 150 accepts 1 sensor signals or information from local room or duct sensors if needed or desired rather than 2 remote sensors. For example, temperature cannot be sensed remotely, since the temperature 3 of the air will change as it moves through the tubing. Additionally, some areas may need 4 instantaneous sensing or the input may not be a sensed contaminant of the air such as the state of a room switch or an occupancy sensor. This is shown in Room 20A where room 6 sensor 25A, which could for example be a temperature sensor, is connected to the sensor 7 inputs block 150 through electrical cable 26A. Additionally optional occupancy sensor 27A, 8 which may provide a digital high/low signal indicating the presence of someone in the space, 9 is connected to sensor inputs block 150 through cable 28A. The sensors and the sensor inputs block may accept many signal forms such as analog or digital. Alternatively, the sensor may 11 have its own onboard microprocessor and communicate with the sensor inputs block 150 12 through a data communications protocol such as, for example, LonTalk by Echelon 13 Corporation, or an appropriate protocol outlined by ASHRAE's BACnet communications 14 standards, or virtually any other appropriate protocol, including various proprietary protocols and other industry standard protocols commonly used to provide data communications 16 between devices within a building environment. Typically, however, when digital data 17 communications are used to connect to discrete devices such as 25A, and 27A, this is 18 accomplished using a protocol operating over a physical layer such as an EIA485 physical 1g layer, on top of which a suitable upper level protocol will be used. In such cases, for example, cable 28A may be specified as a twisted shielded conductor pair.
Nevertheless the 21 connections between sensors 25A and 27A and inputs block 150, may be accomplished using 22 any number of cable types common to the building controls industry.
Additionally, cable 23 28A may be omitted and the sensors 25A and 27A may communicate wirelessly to inputs 24 block 150.
The signal processing controller block 130 is used to process the sensor information 26 from the shared sensors to create virtual sensor signals reflective of the environmental 27 conditions in the sensed locations. This information is added to the information from any 28 local room sensors such as 25A and 27A, and is then used in a variety of possible ways. For 29 example, this information can be sent to building control system 180 for monitoring and or control purposes through a digital networked connection 181. The information interchange 31 could be done using for example, a BACnet protocol, Lonworks, XML data interchange or 32 other suitable interface information conversion. The physical connection 181 could be an 33 Ethernet connection, EIA485 (also known as RS485) connection or other type of digital data 34 communications connection. Another use of the data can be to send it through an internal 1 and or external local area or wide area network for monitoring at a remote location.
2 Additionally, the data can pass directly, or through a local area network, phone network or 3 other suitable connecting means 171 to connect to the Internet or a dedicated network from 4 which a website or other suitable means can be used to remotely access, display, and analyze the data from the multipoint air sampling system 100.
6 Most importantly, signal processing controller block 130 can also provide the control 7 signals 31 and 32 used by the critical environment airflow controller 30 which in FIG. 1 is 8 shown as block 30A, B, and C and dilution ventilation command signals 31A, B, and C plus 9 room offset command signal 32A. Control signal 31 is used to dynamically vary the io minimum air change rate or dilution ventilation level of critical environment 20A, 20B, and 11 20C. The control signal 32 is used to individually, or in combination, vary the offset airflow 12 21A, B, and C of critical environments 20A, B, and C both in magnitude and polarity or 13 direction (positive to the corridor or negative). Also, given the flexible nature of the 14 electronics associated with critical environment controller 30, part or all of the functions performed by signal processing controller 130 may be performed within controller 30, which 16 can be a programmable device. In this case, signals 31 and 32 may at least in part be created 17 within controller 30.
18 Referring to dilution ventilation command signals 31, the signal processing controller i9 block 130 can produce these signals, or portions or all of the control functions can be 2o produced by the building control system 180, as is shown for example in FIG. 2, using sensor 21 information from the shared sensors 220 in FIG. 2 and or the local room sensors 25A and 22 occupancy sensors 27A. Further, it should be clear that signal processing controller 130 of 23 FIG. 1, signal processing controller 210 of FIG. 2, or signal processing controller 420 of 24 FIG.6 need not be physically paclcaged within blocks 100, 200, or 400 respectively and that it's possible to implement signal processing controllers 130, 210 or 420 as either standalone 26 modules, or to integrate them with some other portion within Figures 1, 2 or 6, such as, for 27 example, room sensor 25A. There are several different control approaches for signal 31 that 28 can be implemented by the signal processing controller block 130 of FIG.1 as well as by the 29 signal processing controller blocks 210 or 420 as shown in FIG. 2 or 6 respectively, or by the 3o building control system 180. These control approaches have two important components. One 31 component refers to the type of control approach such as two state, three or multiple states, 32 continuously variable control, or methods involving a combination of both discontinuous and 33 continuous control functions. The other refers to how multiple sensor signals are combined 34 to generate a control signal. Note however, that multiple signals are not required to 1 dynamically vary the dilution ventilation. One signal may be used alone, such as a photo-2 ionization detector (PID) TVOC sensor that picks up a broad range of chemical compounds, 3 to generate the control signal. Many types of PID TVOC sensors exist and are known to 4 those skilled in the art of TVOC sensing. Examples of one type of a PID TVOC
sensor are the RAEGuard PID, the ppbRAE Plus or the MiniRAE 2000 all manufactured by Rae 6 Systems of San Jose, CA.
7 One embodiment of the control approach for dilution ventilation command signal 31 8 is a two state control approach whereby ventilation signal 31 is maintained at it's minimum 9 level, for example at a dilution ventilation value corresponding to, for example, 2 or 4 ACH
xo (or some other appropriate lower value depending on what's suitable for the environinent ii being monitored), unless a trigger event occurs that could consist of a threshold or trigger 12 value being exceeded by the sensor signal. As mentioned before if the sensor signal consists 13 of just one contaminant, a simple threshold or trigger value (corresponding to the value of the 14 sensed contaminant at which some action is to be taken) can be defined.
Alternatively, the trigger could consist of the signal matching in some way a specified signal pattern such as a i6 rapid increase in level even though a specified threshold level was not achieved. The trigger 17 event could also consist of a combination of one or more sets of threshold values and signal i8 pattern pairs, any one of which could constitute a trigger event.
19 If multiple sensor contaminants are being employed such as from the shared sensors 120 and or a local room sensors 25A, the trigger event could be defined as any one of the 21 employed sensor signals exceeding a threshold value, matching a signal pattern, or meeting 22 the conditions of one of potentially multiple sets of threshold level and signal pattern pairs.
23 Each sensor signal would most likely have a different threshold value level and or signal 24 pattern that corresponds to an appropriate value for the sensed contaminant based on accepted levels of that signal related to one or a combination of health, comfort or other criteria of 26 importance for that sensed contaminant. For example, a PID TVOC sensor would likely have 27 a threshold level of about 0.5 to 2 PPM. A level in this range senses many materials below 28 their OSHA TLV (Threshold Limit Value) while still not generating many false alarms by 29 staying above normal levels of less harmful materials such as alcohol vapors. If a particle counter measuring in the range of 0.3 to 2.5 microns is used a level can be set that would not 31 normally be exceeded such as in the range of 1.0 to 5 million particles per cubic feet, yet still 32 pick up the evolution of smoke or some type of aerosol release into the lab room. The specific 33 level could be set based on the level of filtration to the space, i.e. the more the filtration, the 34 lower the level that could be used. Other sensors such as a carbon monoxide, ammonia, .i nitrous oxide, ozone, or other toxic gas sensor can be set directly for the TLV of the 2 compound or for a lower level that would not normally be reached in typical operation.
3 Alternatively, a triggering condition could consist of a combination of two or more 4 sensed air contaminants each reaching or exceeding a given level for that compound or meeting some signal pattern condition. For example, individually, a moderate level of fine 6 particles such as 1.5 million particles per cubic feet, a moderate level of TVOC's such as 0.5 7 PPM, or a moderate level of temperature excursion to above 85 degrees might in themselves 8 not trigger a need for increased dilution ventilation. However, the combination of all three 9 contaminants meeting the preceding conditions could indicate a small lab fire or explosion 1o that would definitely require an increased level of dilution ventilation.
11 A further implementation of a trigger condition involving multiple sensed 12 contaminants could be an additive trigger condition. A good example of this relates to 13 exposure to hazardous materials. OSHA indicates that the effective TLV of a mixture of 14 gases can be computed by adding the fractions of each individual compound's level vs. it's TLV to get the fraction of the combined mixture against the combined TLV. For example, if 16 the system detects that carbon monoxide is at 65% of the threshold limit value and that sulfur 17 dioxide is sensed to be at 70% of its TLV value then although individually neither compound 18 would trigger the system the combination of the two would be at 135% of the combined TLV
1g and as such would constitute a trigger condition. To implement this approach each sensed contaminant of interest would be individually scaled and then added together and a threshold 21 trigger set for the summed result.
22 Another variation on how a trigger condition can be set up is to have the trigger 23 condition vary or be changed based on some other contaminant. For example, a trigger 24 condition could be varied based on occupancy, if no one is in the space, the trigger conditions for some contaminants might be raised slightly. The trigger level could then be lowered when 26 some one is detected or determined in some way to be in the space through, for example, 27 occupancy sensor 27A in Room 20A, a card access system, or other means such as the 28 detection of changes in C02 in the space. There could also be manual local or remote 29 override changes to the trigger levels, based on for example, an increased or decreased 3o concern about the contaminants in the lab. Alternatively, the levels could be changed 31 automatically by the signal processing controller 130, 210, 530, or 420 of FIG. 1, 2, 4, or 6 32 respectively, some other system such as the building automation or building control system 33 180, or a critical environment airflow control system.
1 Finally, any number of different logical or Boolean combinations of sensed 2 contaminant values or sensor signal pattern conditions acting on any number of sensed 3 contaminants affected by any other set of conditions or acted upon by other systems can be 4 used to trigger a need for increased dilution ventilation by increasing dilution ventilation command 31.
6 There are a vast number of control techniques that may be used to generate command 7 31 in order to vary the amount of ventilation within the monitored critical environment 20 in 8 order to dilute the sensed contaminant sufficiently to prevent the concentration of the 9 airborne contaminant from exceeding a specific level. Any method that one may use, from a 1o standpoint of control logic or algorithm, whether it be an open or closed loop strategy i1 involving continuous or discontinuous control functions, fuzzy logic, proportional-integral-12 derivative functions, feed-forward functions, adaptive control, or other techniques known to 13 those skilled in the art of control system design, are considered to be aspects of this invention.
14 FIG. 7A illustrates one possible scenario of steady-state levels associated with command 31 when signal processing controller 130 is configured to provide a two-state 16 control function such that command 31 is increased to an enhanced dilution mode level from 17 a normal level or ACH (air changes per hour) value when a sensed contaminant from critical 18 environment 20 transitions above an established trigger value. Conversely, when the value of 19 the sensed contaminant transitions from a level that's above the trigger value to one below that value, command 31 will drop back to its normal steady state ACH value.
FIG. 7A makes 21 no reference to the time response of command 31 as it transitions from the normal ACH value 22 to the Enhanced Dilution mode and vice versa, as this is a function of the particular control 23 technique used to make such a transition while ensuring that stability is maintained within the 24 system. As an embodiment of this invention the two-state approach of FIG.
7A can be acceptable for use in many applications. However, in some cases the system stability realized 26 with the simple switching mechanism depicted by FIG. 7A will benefit by including 27 provisions to prevent command 31 from oscillating.
28 As an embodiment of this invention, when command 31 is transitioned from the 29 normal ACH value (3-4 ACH, for example) to the enhanced dilution mode (10-15 ACH, for example), command 31 will be latched or become fixed at that higher value, so that following 31 the transition if the measured contaminant drops below the triggered value the air change rate 32 will remain high. Such an approach may be accompanied by some form of notification 33 mechanism from the Building Control System 180, or the sampling system 100, 300, 400, or 34 via the internet connection 171, or from the air flow controller 30 or some other component 1 of the system that airflow controller 30 connects to, which will alert maintenance personnel 2 or other staff that the trigger value has been exceeded so that signal processing controller may 3 be manually reset.
4 As an alternate embodiment, instead of latching command 31 when the value of the sensed contaminant exceeds an established trigger value, one may apply a hysteresis function 6 as shown in FIG. 7B which depicts another scenario of steady-state levels associated with 7 command 31, in which two different triggers or transition points are provided (input low 8 trigger and input high trigger). Here the input high trigger is used when the command 31 is at 9 a level corresponding to the normal ACH value, while the input low trigger is used when the io command 31 is at a level corresponding to the enhanced dilution mode.
x1 An exemplary type of control approach for dilution ventilation command signals 31 is 12 a three state control approach. Unlike the previously mentioned control approach, which had 13 two output levels such as a high level, typically for a purge, and a low normal operating level, 14 this approach has three output levels. A typical application for these three levels would be the same two levels mentioned previously with an intermediate level added that is not for 3-6 spills (an extreme transgression in the levels of a sensed contaminant) but for controlling 17 more moderate levels of sensed contaminants that are desired to be lowered.
For example, if 18 a level of between 1 PPM and 10 PPM from the TVOC detector is sensed, the system would 19 increment up a moderate level, say from a minimum level of 3 ACH to a level of 6 ACH's.
However if the TVOC detector sensed levels above 10 PPM, then the system would go into a 21 purge mode with perhaps 10 to 15 ACH's of dilution ventilation. This approach limits 22 energy consumption for moderate contaminant levels and reduces the chance that if multiple 23 rooms are at this moderate level, that the total system airflow capacity of the building will be 24 exceeded by too many rooms being commanded to maximum air change rate (ACH) value.
Another benefit of a three or other multiple level approach (or of a VAV
approach as well) is 26 that it lessens the chance of realizing an unstable condition where the room airflow can vary 27 up and down due to a steady release of contaminants that alternately is purged to a low value 28 and then slowly builds back up as the system alternately increases and overshoots and then 29 decreases and undershoots the desired dilution airflow command level by an amount that exceeds what is required for a stable operating condition.
31 The three state control approach can be extended beyond three output states to any 32 number of output states for dilution ventilation command signals 31 to provide different 33 levels of dilution ventilation for a space. Finally any of the approaches to use multiple sensed 34 signals such as from the shared sensors 120 and or a local room sensors 25A
can as 1 mentioned previously for the two state approach, also be used for the three or other multiple 2 state control approaches.
3 An exemplary type of control approach for dilution ventilation command signals 31 is 4 a variable air volume or VAV approach. In this approach, once the sensed contaminant signals reach some trigger level or match some signal pattern, the dilution ventilation 6 command signal 31 can increase in a continuous manner from a minimum level which would 7 match the minimum state output of the two or multiple state approach, all the way up to a 8 maximum level that would correspond to the maximum level of the two state or multiple state 9 approach. This effectively "infinite state" approach would as mentioned with the previous lo control approaches work with one or more sensed signals such as from the shared sensors 120 11 and or a local room sensors 25A that could be combined in any manner. One difference with 12 this approach, however, is the need for a "trigger' signal that has a continuous output that is 13 related to the command signal 31. This trigger signal can be formed from one or a plurality 14 of sensed signals such as from the shared sensors 120 and or a local room sensor 25A as has been described previously.
16 A linear or non linear relationship can be established between this trigger signal and 17 the command signal 31. For example with a linear relationship an offset and simple scale or 18 gain factor can be used as well as a minimum and maximum clamp so that as the trigger 19 signal increases above the minimum command signal value, the command signa131 will increase as well until it hits the maximum allowed command signal value. One of the reasons 21 to use a VAV approach is to create a closed loop control of the IEQ within the monitored 22 space so as to prevent an oscillating control pattern that might be generated in some situations 23 by a two state approach. With the VAV approach an increased ventilation level could be 24 maintained between the minimum and maximum command signal 31 levels without an oscillating command level, particularly where there is a roughly constant level of 26 contaminant emission. This approach could be used to regulate the level of an air 27 contaminant such as a TVOC, particulate, or other at a certain setpoint rather than drive it to a 28 minimum level that could prove to be costly in terms of the energy expense of running at 29 high ventilation for extended periods. This approach could be appropriate when the contaminant is not a particularly hazardous one and can be set to be maintained at a level that 31 would not create a health impact such as particles.
32 Alternatively this VAV approach could be used for another purpose with C02 levels 33 being sensed and used to set a given minimum ventilation rate related to the occupancy or 34 number of people in the space such as given amount of outside air or cfni per person to meet i certain building codes and guidelines such as those referred to in ASHRAE
standard 62-2004 2 versus to control to a given contaminant level. This can be done since there is a fixed 3 relationship between the level of C02 in a space compared to the amount of people in that 4 space divided by the amount of outside air introduced into the space. This type of control is sometimes referred to as demand control ventilation and has been used in office 6 environments to allow outside air rates in facilities that use recirculated or return air to 7 approximately track occupancy levels to a level such as for example 15 to 20 cfin per person.
8 In this control approach C02 is used as a proxy for directly measuring the cfm per person 9 ventilation level due to the fixed amount of C02 exhaled by people, approximately .01 CFM
io per person for a person doing light office work, providing a means to effectively measure the 1i number of people in a space divided by the outside air introduced into that space.
12 In a VAV contaminant control approach where the contaminant is controlled to a set 13 point value, alternatively, instead of only one signal, multiple of air contaminant signals may 14 be combined or added, using methods similar to those mentioned earlier, to generate a single mixed or blended contaminant signal that can then itself be controlled to a setpoint value.
16 FIGs. 8A and 8B show another embodiment which is a generalized view of a closed 17 loop system 900 used to provide dilution ventilation control by varying the air change rate 18 within a critical environment, such as 20, in a continuous (or VAV) fashion within prescribed 19 limits in order to prevent the level of a sensed contaminant, such as TVOC's for example, from exceeding a prescribed value. Here, sensor feedback 908 is subtracted from contaminant 21 set point 901, which represents the level of the sensed contaminant that system 900 is to 22 control to, in order to (by error stage 902) create error signal 914. Error signal 914 is acted 23 upon by control block 903 in order to create a term that is bounded by Min ACH Clamp 24 block 904 and Max ACH clamp 905 in order to yield command 31, which is the command to air flow block 906, which is composed of air flow controller 30 and the exhaust and supply 26 flow (42 and 52) that it controls. Also depicted in FIG. 8A is block 907, which represents the 27 dilution characteristics of the critical environment. For those who are familiar with the art of 28 control system design, 907 represents the transfer characteristics of the environment which in 29 this case defines how the air change rate of the environment under control relates to the value of the sensed contaminant 908. Here, error stage 902, reverse acting control block 903, Min 31 ACH Clamp 904, and Max ACH clamp 905 may be implemented within signal processing 32 controller 130, or within Building Control System 180.
33 Control block 903 may be implemented using any of a large number of control 34 strategies known to those who are skilled in the art of control system design and may as an i example include any combination of proportional control, proportional-integral control, 2 proportional-integral-derivative control, feed forward techniques, adaptive and predictive 3 control, and fuzzy logic strategies. One of the essential elements of control block 903 is that it 4 provide the necessary reverse acting and level-shifting functions so that it may properly act upon error signal 914 (given the subtractive logic shown for error stage 902) in order to 6 create a command term 31 which will yield an increase in the critical environment's air 7 change rate at least for the condition where the sensor feedback 908 exceeds the contaminant 8 set point 901. (Alternatively, the logic of 902 could be altered so that 901 is subtracted for 9 908.) As an example, contaminant setpoint 901 may be set to 1.5 ppm and the sensed contaminant may be, for example, TVOC's (using, for example a photo-ionization detector -11 or PID sensor-). Control block 903 will be configured so that when sensor feedback 908 is 12 less than setpoint 901 the output of 903 will be less than or equal to the minimum clamp 13 value established by minimum ACH clamp block 904. 904 is a"high-select"
block in that it 14 will compare the value of the output of 903 to some minimum clamp value (4 ACH, for example) and present the larger of the two values to the next block 905. For example, if the 16 output of 903 is 2 ACH and the minimum clamp value set in 904 is 4 ACH, the output of 904 17 will be 4 ACH. The output of 904 is presented to Max ACH clamp 905 which provides a 18 "low-select" function in that it will compare the value of the output of 904 to a prescribed 19 "max clamp" value (12 ACH, for example) and output the smaller of the two to air flow block 906. The way the system 900 works is that if there is some sudden increase in the level 21 of the sensed contaminant (due to a spill in a laboratory, for example) above the contaminant 22 setpoint 901 (set to 1.5 ppm TVOC's for example) the control block will (within the 23 limitations of max clamp 905 set to 12 ACH, for example) increase command 31 to the value 24 necessary to limit the TVOC concentration within the controlled environment to 1.5 ppm. In practice, set point 901 can be set to a value less than the TLV for the contaminant to be 26 sensed to insure that sustained concentrations will be limited to a steady-state value that is 27 safe. Alternatively, contaminant set point 901 may have a dynamic value that adjusts based 28 on the persistence of the contaminant monitored by 908.
29 FIG. 8B illustrates an alternate embodiment of system 900 that provides the same control functions as FIG. 8A, but for any number "n" of contaminants. With this approach, a 31 dedicated error stage 902 and control function block 903 are provided for each sensed 32 contaminant (1 through "n"), with the nth sensed contaminant's set point shown as signal 909 33 going to error stage 910 which has an output 915 that is processed by function block 912.
34 The outputs from each control block, such as from control blocks 903 to 912, are presented to 1 high select block 913, which passes the largest of the control terms from the control blocks to 2 airflow block 906 as command signal 31. Using this approach, one can provide dilution 3 ventilation control to an environment such as 20 based on a number of contaminants, such as 4 TVOC's, particles, and a host of other contaminants with individual setpoints such as 901 to 909 for each monitored contaminant.
6 An implementation of a portion of the signal processing logic of the signal processing 7 controller block 130 in FIG. 1, or of block 210 in FIG. 2 is shown in signal processing 8 controller block 530 in FIG. 4. In this diagram the control functions can be implemented in 9 analog or digital logic or be implemented with computer software or a firmware program or io any combination of these. In FIG. 4, shared sensors 520 create one or a multiple of output 1i signals or variables shown for example in the diagram as sensor signals 525, 526, and 527 12 representing the outputs of individual sensors C02, CO, and TVOC's respectively. Although 13 FIG. 4 illustrates the use of these three sensors, any number or type of sensors can be used.
14 Since the sensors are being multiplexed with the air samples from multiple rooms, three in this example, the individual or "virtual" sensor signals for a given room corresponding to, as 16 mentioned previously, a sensor signal or represented software variable for a given air 17 contaminant in that room or area must be de-multiplexed from the signal stream of that 18 contaminant. This is done within signal processing controller 530 by the de-multiplexers 531, Ig 532 and 533 that de-multiplex the C02, CO, and TVOC sensor signals respectively using the 2o control signals 511 from the control logic block 510. Block 510 corresponds to control logic 21 block 110 in FIG. 1 as well as part of signal processing controller block 210 and part of 22 control logic block 310A, B, and C in FIG. 2. The output of the de-multiplexing blocks 531, 23 532, and 533 are individual or "virtual" sensor signals or software variables that represent the 24 sensed contaminants or other air characteristics or air quality parameters for rooms 20A, B
and C. For example, signals 522A, B and C represent the signals or variables for the sensed 26 C021evels in rooms 20A, 20B and 20C, respectively.
27 These virtual sensor signals will typically have a value representing the last de-28 multiplexed value that will be held constant at that level until the next sampling of the 29 corresponding location for that signal. At this point the signal will change value to equal the 3o new de-multiplexed value. This transition of state from one de-multiplexed value to the next 31 de-multiplexed value can occur either as a rapid or approximately step change in signal or it 32 may occur gradually in a ramped manner lasting from several seconds in time up to inany 33 minutes depending on the desired properties of the virtual signal, what is being controlled 1 with that signal, and how often the location is being sampled. A preferred approach would be 2 to have a gradual change of value occurring over between 5 and 60 seconds.
3 If we again focus on the variables for Room 20A, then the signals for C02, CO, and 4 TVOC are 522A, 523A, and 524A respectively. As mentioned previously these individual or virtual sensor signals 522A, 523A, and 524A can then be modified with an offset and scale 6 factor block 534A, 535A, and 536A respectively as needed or some other control function 7 can then be applied. These modified signals from blocks 534A, 535A, and 536A
are then 8 acted upon by function block 537A. This is the block that may add these signals together, 9 take the higher of the signals, apply threshold value or signal pattern trigger functions to the xo signals individually or as a group, or apply some other approach to combine or use these ii signals as mentioned previously. The result of block 537A after it has applied appropriate 12 trigger criteria, some form of non-linear or linear scale and offset criteria, control loop gain 13 function, or some other control or Boolean logic is to create a two state, three or multiple 14 state, or a VAV dilution ventilation command signal. Finally, this command signal or control variable may then be outputted to a building control system or to another system as either a 16 digital signal or variable such as signal 538A or as an airflow command signal or software 17 variable such as the dilution ventilation airflow command signal 31A
created by output block 18 540A and used as an input to room 20A's critical environments airflow control block 30A.
19 One other function that may be implemented within Function block 537A is a time 2o delay or ramp function. For example, when a threshold value is exceeded, then the output of 21 function block 537A which will become ventilation command signal 31A could be increased 22 to it's maximum or purge value that might correspond for example to a room air change level 23 of between 10 to 16 ACH's. This increase in value can occur instantly or may be commanded 24 to be a gradual ramp by function block 537A. Such a ramp or slowly increasing signal could occur over the span of a minute or more. This might be done so as to not make an 26 objectionably rapid increase in the room's flow level or cause problems with the control 27 system trying to keep up with a rapidly changing signal that could cause a pressurization 28 problem if the supply and exhaust control devices can not keep up with the changing signal.
29 Similarly, when the ventilation command signal is meant to drop from a higher level such as 10 ACH down to a lower or minimum level such as 4 ACH, the function block 537A
could 31 create a slow ramp that gradually decreases the output signal 31A over some period of time 32 such as one minute or more.
33 Similarly these increasing or decreasing ramps or gradual changes in level could be 34 made linear, with constantly increasing or decreasing rates or made non-linear such as with 1 an exponentially changing rate so the ramp could start faster and gradually slow down or 2 conversely start slowly and gradually increase its rate of change in value until the signal hits 3 it final value. These ramps could also be at different rates based on whether the signal is 4 increasing or decreasing. For example, it may be advantageous to rapidly increase the dilution ventilation of a room by rapidly increasing the dilution ventilation command 31 if a 6 spill or large increase in the contaminant level in the room is detected.
However, it may also 7 be helpful to have a slow ramp downward; perhaps taking 5 to 15 minutes to gradually come 8 down in dilution ventilation flow to malce sure that the contaminant is removed even to a 9 level below the threshold of detection.
In an alternative to ramping the changing flow over a large signal range, it may, for 11 the same reasons mentioned above, be desirable to change not just the rate of change of the 12 dilution ventilation command 31 created by the signal, processing block 530 and function 13 block 537A within it, but also the amount of the step change possible based on a change in 14 the sensed air contaminants such as from the shared de-multiplexed sensor signals 522A, 523A, and or 524A. In other words, rather than allow a full slew from the minimum dilution 16 rate to the maximum dilution rate from one air sample measurement, it may be desirable to 17 limit the maximum step change in dilution ventilation airflow. For example a maximum step 18 change size could be set for an increase in airflow representing four ACHs in a possible range 19 from a minimum of four ACH to a maximum of sixteen ACH. With the maximum step size set for example for four ACH, it would take three successive air samples to have air 21 contaminant values in excess of the trigger values to boost the dilution command 31 from the 22 minimum to it's maximum value. Similarly, if the maximum reduction was also limited to a 23 flow rate equal to four AC it would take three successive measurements of the critical 24 environment's air contaminants to be below the trigger value for the dilution command level to drop from a level corresponding to sixteen ACHs down to four ACH.
26 In a manner similar to the ramp approach mentioned above, the increasing and 27 decreasing step heights may be of different sizes. For example, to respond quickly to a spill 28 there may be no limit or a larger limit for an upward or increasing change in dilution 29 ventilation command 31. However, to ensure a large amount of dilution to very low levels and reduce the possibility of an oscillation if the source is not a spill, but a continuous 31 emission, it may be advantageous to have a smaller decreasing step change size to hold the 32 dilution ventilation at a higher level for longer periods so it takes several air sample cycles to 33 fully reduce the ventilation level to its minimum level.
1 Another means to set the step heights or possibly the ramp rates is based on the level 2 of detected contaminants or their rate of change. If a large value of contaminant and or a 3 rapid rise in its level is detected since the last sample or recent samples, it may be 4 advantageous to use different step change heights or ramp rates. For example in a spill, where there is a sudden increase to a large contaminant value, it may be prudent to immediately 6 index the dilution command 31 to its maximum value. Smaller or more gradual increases in 7 value could be set for smaller steps. On the other hand a sharp downward increase might not 8 change the downward step level in order to keep the ventilation higher to better clean the air.
9 Alternatively, for energy saving reasons and or if there happens to be many brief upward xo excursions of contaminant levels that may not be hazardous, it may be more beneficial, if the ii contaminant level has just rapidly dropped to below the trigger level to quickly drop the 12 ventilation command 31 to its minimum level. As such, it may also be beneficial to have 13 different step or output characteristics associated with each air contaminant. As a result, the 14 output control characteristics would be different based on which air contaminant(s) triggered the need for more dilution ventilation.
16 Output signals of the signal processing controller block 530 may also be used to 17 change the sampling sequence based on the detection of a spill or a level of contaminant that 18 is of interest to more closely observe. In this alternate approach the sequencing of air samples 1g into the shared sensors from the critical environments 20 may be altered through signal processing controller block output signal 512 that is used by control logic block 510 to 21 modify the sampling sequence on a potentially temporary basis during the period of a 22 detected event of interest in a particular space 20. Based on seeing the control signal or 23 software variable 512 increase in value to some higher trigger level or exhibit some signal 24 pattern such as a rapid rise in amplitude, the control logic block 510 might increase the frequency of the air sampling of the space where the event was detected.
Alternatively or 26 additionally, the areas around the affected space may be quickly sampled next or sampled at a 27 higher frequency as well to look for a spread of the contaminant to other spaces. In the 28 context of this invention a rapid rise in amplitude can be defined as a sudden increase in 29 value to a level such as many times larger than the normal trigger level in less than 5 minutes such as that seen due to a spill of a volatile organic compound.
31 This change in sampling or control sequence can be implemented with the sampling 32 system of either FIG. I or FIG. 2. If the latter system was being used, the detection of the 33 event would be most likely carried out by the signal processing controller block 210 and the 34 change in sequencing carried out by control logic blocks 310A, 310B, 310C
1 Another change in control sequence that could be implemented if an event of some 2 type is detected in a space or several spaces would be to change the sampling sequence by 3 adding air sampling of several spaces at once to measure a mixed sample of several rooms.
4 This could be implemented for example, by turning on one or more solenoids at once to gather a mixed sample of affected areas or of multiple areas nearby the affected area to 6 rapidly look for potential spillage into other areas. This would be implemented in the same 7 manner as mentioned above but would involve turning on multiple solenoid valves such as 8 for example solenoids 161, 162, 263, and 164 in FIG. 1 or solenoids 361A, 362A, 363A, and 9 361B in FIG. 2.
With reference to FIG. 2, this diagram refers to another preferred embodiment of the 11 present invention directed to dynamic control of dilution ventilation in one-pass, critical 12 environments using a networked air sampling system such as one similar to that described in 13 U.S. Patent No. 6,125,710. This sampling system has many of the functions and is similar to 14 the system indicated in FIG. 1 with the main difference being that the solenoid switches and some of the controls are distributed throughout the building vs. being located in one central 16 unit. As a result, central sampling unit 100 shown in FIG. 1 is effectively replaced by sensor 17 and control unit 200, along with distributed air and data routers 300A, 300B, 300C, and 18 300D. The control of the sequencing of the system and the signal processing functions are 19 handled by signal processing controller block 210. This block 210 carries out the functions of 2o blocks 510 and 530 in FIG. 4 that have been described previously. The shared sensor block 21 220 carries out the same function as block 520 of FIG. 4 and block 120 of FIG. 1.
22 Blocks 300A, B, C and D are air and data routers that house the solenoid valves 23 361A, 362A, 363A, 361B, 362B, 361C and 361D as well as potentially some analog or 24 digital input and output capabilities that are contained in Input/Output blocks 320A and 320B. As an example, air sampling location 23A is connected via tubing or air transport 26 conduit 24A to solenoid 362A that is part of air and data router 300A. This tubing or air 27 transport media 24A along with 44A, 14, 44B, 54B, 24C and 64 was described earlier except 28 that the air transport conduit may also have associated with it some additional electrical 29 conductors for the purpose of adding networked data communication, low voltage power, signal wires and other potential functions as described in U.S. Patent Application Serial No.
31 10/948,767, filed on September 23, 2004 entitled, "TUBING FOR TRANSPORTING
32 SAMPLES IN AN AIR MONITORING SYSTEM", as well as U.S. Patent Application Serial 33 No. 11/149,941 filed on June 10, 2005 and entitled, "AIR MONITORING SYSTEM
1 TRANSPORTING AIR SA.MPLES". Adding these conductors enables local sensors to be 2 conveniently and cost effectively added to the system.
3 For example, sampling location 23A, as well as the other sampling locations 43A, 4 43B, 53B, 24C and 63, could also contain a local temperature sensor to sense the room or duct temperature. The signal from this temperature sensor or from other sensors such as 6 humidity, or other air characteristics can be sent to the air data router 300 as a digital data 7 communications signal though a data communication cable such as a twisted pair, twisted 8 shielded pair, fiber optic cable or other digital data communications media.
Alternatively, the 9 sensor information could be sent to the router 300 via an analog signal through one or more signal conductors as an analog voltage or current signal. This analog signal can then be ii converted to a digital signal by the I/O block 320A or 320B in the router 300A or 300B
13 These I/O blocks 320A and 320B can also monitor other air contaminants or signal 14 inputs that are not associated with an air-sampling inlet yet would have a data communications cable, analog signal cable or other connection to the I10 block. An example 16 of these sensors is Room Sensor 25A which could be a temperature sensor, an air 17 contaminant sensor or other type of sensor such as a light, differential pressure, air velocity or 18 other building sensor, as well as the occupancy sensor 27B, occupancy switch 28C, or 19 emergency exhaust switch 81. Of the latter sensors or room switches, an occupancy sensor is 2o defined in the context of this invention as a sensor that can detect the presence of people in a 21 space through infra red energy, motion, card access, or other means, whereas an occupancy 22 switch is defined in the context of this invention as a room switch such as a manually 23 operated light switch or other type of room switch operated by the occupant when they enter 24 or leave the space. A room switch in the context of this invention is defined as some type of switch that may be for example electrical, mechanical, photonic, or pneumatic that is located 26 in or near the critical environment that can be manually operated to signal a change in state to 27 a system connected to it. An emergency exhaust switch is defined as a room switch such as 28 an electrical wall switch that can be thrown or actuated by the occupant when an emergency 29 event has happened such as a fire, spill or explosion. The emergency exhaust switch may 3o affect some outcome such as to provide maximum dilution ventilation to the space and or 31 potentially provide a containment action by increasing the negative offset of the space or it 32 may be for monitoring only. This room switch as well as some others may for convenience of 33 sharing wiring be located in the same room location and possibly in the same enclosure as the 1 air sampling pickup. Other types of room switches or sensors could also be connected to the 2 UO blocks 320 of the air and data routers 300.
3 Within the air data routers 300, the output of multiple solenoid valves can be 4 manifolded together with manifold 390A and B. These manifolds plus the outputs of individual solenoid valves such as 361C in air and data router 300C or solenoid 361D in 6 router 300D are connected together with tubing or air transport conduit 202 to transport air 7 samples to shared sensors 220 in the multipoint air sampling unit 200 as moved by vacuum 8 source 140. The control of the air and data routers as well as the communication of digital 9 sensed air characteristic and contaminant data from the I/O blocks within the routers or from the local sensors in the spaces back to the multipoint air sampling unit 200 is through data 11 communications cable 201. The air transport media 202 can be constructed using the same 12 materials mentioned previously for tubing 24A and other connections from the spaces 20 to 13 the routers 300. The data communications cable 201 can be made with any commonly used 14 data communications media such as twisted pair, shielded twisted pair, fiber optics cable or other. Additionally in a preferred embodiment the air transport media 202 and the data 16 communications media 201 can be combined into one structured cable as was described for 17 the connections between the rooms 20 and the routers 300.
18 As in FIG. 1 the multipoint air sampling unit 200 also connects to the Internet 170 to 19 send information about the critical environments to a password protected website for review 2o by the occupants or facility personnel. Again as in FIG. 1 the multipoint sampling unit 200 21 can also interface to and send data back and forth through data communications media 181 22 with the facility's building control or management system 180. This can be done directly or 23 through one of many interface protocols such as BacNet, Lon by Echelon, XML, OPC, or 24 others.
In addition to the air and data routers 300 that can accept sensed input signals from 26 the spaces 20 and provide signal outputs 31 and 32 to help control the rooms 20, the building 27 control system 180 can also be used to accept various sensor input signals such as 29C from 28 occupancy switch 28C and signal 82 from emergency exhaust switch 81. This information 29 can be used by the building control system directly for control and also communicated back 3o to the multipoint air sampling system 200. The building control system 180 can also provide 31 control signals to help control the airflow in rooms 20 as shown by signals 31C, and 32C to 32 the critical environments airflow control block 30C using sensor information from the 33 multiplexed air sampling system 100 or 200 and potentially locally sensed signals, room 34 switch information, as well as other building information.
1 FIG. 3 illustrates a more detailed diagram of one of the critical spaces and some of the 2 airflow control and feedback devices and signals used therein. In addition to the components 3 that have been described previously, this diagram also shows the room exhaust airflow 4 sensing and control device or devices 41 and room exhaust airflow control signa147 as well as room exhaust feedback signa148. Also included is supply airflow sensing and control 6 device or devices 51 and supply airflow control signal 57 and supply airflow feedback signal 7 58. A new device that has been shown is local temperature sensor 91 that communicates 8 through cable 92 to a temperature controller 90. This temperature controller could be part of 9 building control system 180, a stand-alone system, or part of a separate system that controls lo the airflow in a critical environment. Such a control system that includes for example special n exhaust, room exhaust, and supply airflow controller devices 71, 41, and 51 respectively of 12 FIG. 3 as well as the critical environment airflow controller 30 and controls at least room 13 pressurization by maintaining either a given room pressure or volume offset is referred to in 14 the context of this invention as a critical environment airflow control system which may also in some cases be referred to as a laboratory airflow control system. The purpose of 16 temperature controller 90 is to provide temperature control which can include sending a 17 thermal load or temperature command 93 to the critical environment airflow controller 30 to 18 increase or decrease the supply airflow into space 20. The temperature contro190 may also 19 control a reheat coil to increase the temperature of the supply air fed into the space 20 or perimeter heating coils in space 20 for further means of temperature control.
21 Another element not shown in FIG. 1, 2, and 6 is the addition of a special exhaust 22 airflow control and sensing device 71. This control device is connected to a special exhaust 23 duct 70. Special exhaust device 72 could be one of many special exhaust devices such as a 24 laboratory fume hood, snorkel exhaust, canopy hood, chemical storage cabinet, bio-safety cabinet, animal cage exhaust, or other device that exhausts air from the critical environment.
26 Typically the flow of these devices is either fixed, two state or variable based on some aspect 27 of the device. For example the flow through a laboratory fume hood can be made variable 28 and proportional to the size of the fume hood sash opening to maintain a constant face 29 velocity. This type of control can be seen in FIG. 3 where the special exhaust device 72 controls the special exhaust airflow control device 71 through airflow control signal 77. The 31 special exhaust feedback or sensed airflow signal 78 is sent to the airflow controller block 30 32 along with potentially one or more other special exhaust air flow feedback signals illustrated 33 for example by feedback signa188.
1 FIG. 5 is an exemplary embodiment of the control diagram for the critical 2 environment airflow controller 30. The supply airflow within a one-pass critical environment 3 space is set by the higher of either the makeup air required by the space's special exhaust 4 flows, the room's supply airflow requirement to meet the temperature command or the requirements for dilution ventilation in the space. This is implemented as shown in FIG. 5 by 6 first summing any and all special exhaust feedback signals such as flow signals 78 and 88 by 7 summing block 33. This totalized special flow exhaust feedback signal is then provided as 8 one input into the high select signal comparator 34. Block 34 acts to take the highest of the 9 three signals provided to it, passing which ever of the three signals is highest at any given 1o time. The next input into high select block 34 is the temperature command 93 for varying 11 supply flow which is then scaled and offset as needed in scaling block 38 to put it on the 12 same scale factor as the other two airflow command signals inputs, such as certain number of 13 cfm per volt for an analog voltage signal or scaled directly into a given set of units such as 14 cfm or liters per second for a software or firmware variable representing airflow. The third i5 signal is the dilution ventilation command signal 31 which is generated with the assistance of 16 the multipoint air sampling system, the discrete local sensor system of FIG. 6, or the building 17 control system 180 and is again scaled and offset as needed by scaling block 39 to put this 18 command on the same scale factor as the other signals.
lg The command 57 for the supply airflow control device 51 is further shown created by 20 taking the output of the high select comparator block 34 and subtracting offset signal 32 from 21 it by subtraction block 37. The room offset airflow command 32 could be a fixed offset such 22 as 10% of the maximum supply or exhaust cfm, or it could be a signal that varies in a two 23 state, multi-state, or VAV fashion. The purpose of this offset airflow is to create a typically 24 slight negative pressure for the room, although in some applications the offset airflow 25 polarity can be flipped to instead create a net positive pressure in the space vs. the corridor 26 and or other spaces. An exemplary application of the room offset airflow command 32 being 27 a two state control signal is for signal 32 to be a value such as 10% of the maximum supply 28 volume for normal room operation. However, when a spill or other emergency condition is 29 detected such as a fire or smoke release via some sensor, alarm system, or manually with an 30 emergency exhaust switch 81, the room offset airflow can be increased from its normal value 31 by the sampling system, building control system, or the system of FIG. 6.
Increasing the 32 offset airflow to a potentially much higher value will reduce the supply airflow volume so as 33 to create a large negative offset airflow for the room to provide a measure of increased 34 containment to prevent the spread of the spill vapors or smoke into other spaces.
1 Finally FIG. 5 shows an embodiment of how command 47 for the room exhaust 2 airflow control device is created by first starting with the supply flow feedback signal 58.
3 The sum of the special exhaust feedback signals 78 and 88 is subtracted from the supply flow 4 feedback signal 58 and added to the room offset airflow command 32. The resultant signal is the room exhaust command signal 47 that is used to set and control the flow of the room 6 exhaust airflow control device 41.
7 FIG. 6 shows yet another facility monitoring system embodiment of the invention that 8 uses only individual space or duct sensors located in the spaces or ducts to be monitored with 9 no centralized sensing of the embodiments of FIG. 1 or 2. This embodiment can also combine and use the outputs of a plurality of room sensors such as 425A and 427A or others 11 located in room 20A or in the room exhaust duct 40B of room 20B for dynamically varying 12 the dilution ventilation of a one-pass critical environment 20 such as a laboratory or a 13 vivarium. These one or more sensor outputs from the same space or sensor outputs from 14 multiple locations can be combined as mentioned previously or used in a differential manner.
Describing the embodiment of FIG. 6 in more detail, room 20A contains two local or 16 room sensors 425A and 427A. These sensors are connected via cables 426A 4nd 17 respectively to I/O block 430A of the data acquisition and controller block 400A. These 18 cables could be of many different media depending on the output of the sensor. For example, 1g if these or other sensors have current or voltage outputs, analog signal wires could be used for the cables. If the output of the sensors 425A and 427A, or any other sensor, is a digital signal, 21 then typically a twisted pair or shielded twisted pair would be used. If the output was of a 22 digital optical or light signal then a fiber optic cable could be used for these and other local 23 room sensors in FIG. 6.
24 Room sensors 425A and 427A could be one of many different sensors. For example, they could be a particle counter and a TVOC sensor or else they could be two or more of any 26 of many other types of sensors as mentioned previously such as CO, C02, ozone, radon, 27 other toxic gases, ammonia, humidity, dew point temperature, light, differential pressure, etc.
28 Additionally, room 20B in FIG. 6 shows the use of local duct sensors such as 29 individual sensors 443B and 445B mounted in the room exhaust duct 40B as well as local duct sensors 543B and 545B mounted in supply duct 50B. These four sensors are shown 31 connected into I/O block 430B of data acquisition and controller block 400B
through cables 32 444B, 446B, 454B, and 456B respectively. Similarly, room 20C shows the use of room 33 sensors 425C and 427C that are connected to I/O block 430C of data acquisition and 34 controller block 400C through cables 426C, and 428C. I/O block 430C also is monitoring 1 duct sensors 463 and 465 that are mounted in an outside air duct to measure outdoor air 2 conditions. These sensors 463 and 465 are connected to UO block 430C through cables 464 3 and 466 respectively. Any of the sensors shown in FIG. 6 could be used to sense any one or 4 more of the many air contaminants mentioned above or any other type of air contaminant, air characteristic, or building paran7eter of interest that can be sensed.
Additionally, although not 6 shown in FIG. 6, any of the room switches or room sensors shown in FIG. 1 or 2 such as 7 occupancy switch 28C, emergency exhaust switch 81, occupancy sensor 27B, etc. can also be 8 used with the embodiment of FIG. 6 by connecting these switches or sensors into one or more 9 of the inputs of the I/O blocks 430.
In FIG. 6 the data acquisition and controller blocks 400A, 400B and 400C also ii contain control logic blocks 410A, 410B and 410C respectively. These control logic blocks 12 are used to control the functioning and logic of the data acquisition and controller blocks 400 13 as well as help communicate and interface through communications cable media 401 with the 14 other data acquisition and controller blocks and or with another building system such as the building control system 180. The data communications media 401 as well as 201, 181, and 16 171 can be defined in the context of this invention as a data network or communications cable 17 which is part of some form of digital data communications network implemented for example 18 with Ethernet or RS385 cable that runs a communications protocol such as BACnet, 19 Lonworks, or a building controls or other building communications protocol such as Johnson Controls' Metasys N1 or N2 bus. Alternatively, an IP or Internet Protocol could be used.
21 The I/O block 430A like block 320A in FIG. 2 plus signal processing block 420A are 22 also used to create analog or digital airflow control signals 31A and 32A
for room 20A. In 23 room 20B, the signal processing controller block 420B also generates a dilution ventilation 24 airflow control signal 31B as an input into critical environment airflow controller 30B, however in this example, the controller 30B is a networked control device and receives all of 26 its control and feedback signals via communications network 401. For this embodiment the 27 airflow control signal 31B is in the form of a software variable or other form of digital 28 information that is addressed to and received by the critical environments controller 30B.
29 This type of networked control command 31B could likewise be employed in the 3o embodiments of FIG. 1 or 2 using for example the digital communications media 201 of FIG.
31 2 or the building controls communications media 181 of either FIG. 1 or 2.
32 In a similar manner any of the airflow control devices, air contaminant sensors, or 33 controllers described in FIG. 1, 2, and 6 could be networked digital devices whereby the 34 control, feedback, and sensor signals could be digital information communicated between the 1 devices via a networked communications systems such as a private LAN or local area 2 network such as Ethernet or Arcnet, or even via a public communications network such as the 3 Internet.
4 FIG. 6 also indicates how a critical environment airflow controller such as 30C can receive its control signals 31C and or 32C through the building control system 180 that is in 6 communication with the data acquisition and controllers 400. Alternatively, all the data 7 acquisition and controller functions indicated in FIG. 6 may be implemented and performed 8 by building control system 180 without need for a separate data acquisition and control 9 system such as indicated by separate blocks 400. In this latter case the controllers indicated 1o by 400 would be implemented by building control system controllers or through other control 1i or networked devices with control inputs and outputs of the type commonly manufactured 12 and used by building control companies such as for example Johnson Controls with their 13 Metasys system, Honeywell with their Alerton subsidiary's native BACnet system BACtalk, 1.4 or Siemens with their Apogee system.
The signal processing controller blocks 420 or similar blocks implemented with the 16 building control system 180 are used to combine the outputs of multiple air contaminant 17 sensors using the same approaches mentioned earlier for the embodiments of FIG. 1 and 2.
18 Similarly the dilution ventilation control signal 31 and the offset airflow control signals 32 19 can be created using the same methods mentioned earlier and can be of an output type such as two or three state or VAV as mentioned before for the systems of FIG. 1 and 2.
Additionally 21 any of the control or sensing approaches, or control inputs or outputs mentioned in FIG. 1, 2 22 or 6 can be applied to the systems or approaches of the other figures.
Similarly these same 23 approaches or systems can be applied to a facility monitoring system embodiment similar to 24 that of either FIG. 1 or 2 that is implemented not with a multipoint air sampling system but instead using a fiber optic light packet sampling and sensing system such as described in US
26 Patent # 6,252,689 and referred to in this patent as a networked photonic sampling system.
27 Using the systems of FIG. 1, 2, or 6, or the networked photonic sampling system, 28 there are several beneficial control implementations and methods that can be implemented to 29 solve problems that occur when trying to vary the dilution ventilation in a one-pass critical environment. For example, the outdoor air that is being brought into the building may 31 become slightly or significantly contaminated by one or more air contaminants. Such 32 contaminants could include carbon monoxide from auto or truck exhaust or from re-33 entrainment of furnace or boiler exhaust, high levels of outdoor particulates, TVOC's that 34 could be re-entrained from fume hood or other special exhaust stacks, or other outdoor 1 sources of contaminants. If these contaminants are not filtered out and pass into the supply air 2 that is being fed into the labs it could trigger the dilution ventilation controls to increase both 3 the room exhaust and supply air flows. Similarly, the increase in supply air contaminants may 4 not be high enough to trigger increased supply air flow commands by itself, but added to existing contaminant levels in the room it may make the system overly sensitive to low or 6 moderate contaminant levels originating from within the room itself. Both of these problems 7 can produce potentially runaway results since the control action of increasing supply air 8 which contains air contaminants only serves to increase the level of contaminant within the 9 room. This can drive the supply airflow levels even higher until no matter whether a two state, three state, or VAV approach is used the supply airflow into the room will eventually 11 be commanded to its maximum level if the outdoor air or supply system contamination is 12 high enough. Since the supply system airflow potentially feeds many rooms, potentially all of 13 these rooms could be pushed to their maximum flows. This could result in the airflow 14 capacity of the supply and or room exhaust system being exceeded with resultant reductions of flow into and out of the critical environment spaces and potential loss of pressurization 16 levels of these spaces vs. the corridor or other rooms. If the special exhaust devices are also 17 exhausted by the room exhaust fans, then these devices may lose capture and containment of 18 hazardous fumes or vapors.
ig One exemplary control approach to solve this problem is to use a differential measurement technique. In this approach an outside air or supply air measurement is 21 subtracted from room air measurements to create differential measurements of the various air 22 contaminants of interest vs. either outside air or the supply air. Thus, if the outside or supply 23 air has an increase in particles, CO, TVOC's, etc., the quality of the room air will be 24 evaluated against sources of contaminants in the room only since the effect of the supply air sources will be subtracted out. Effectively, we are concerned here not with the absolute 26 quality of the room air but whether it is being made worse by sources in the room or space 27 only, since increasing the dilution air will not make the room cleaner if the dilution air is the 28 source of the contaminant.
29 For example, as mentioned previously, we first start with air contaminant measurements of the air in space 20A using for example room sampling location 23A, room 31 exhaust air duct sampling location 43A, and or room sensor 25A in FIG. 1 and 2, or room 32 sensors 425A, 427A, and or room exhaust duct sensor 443A of FIG. 6. In this exemplary 33 approach a measurement of the air contaminants is next made of either the outside air using 34 air sampling location 63 in FIG. 1 or 2 or air contaminant sensors 463 and 465 of FIG. 6 in 1 outside air intake duct 60 or the supply air using air sampling location 53B
in FIG. 1 or 2 or 2 supply airflow duct sensors 543B and 545B in supply airflow duct 50B. If the spaces are 3 receiving 100% outside air directly from outdoors with no return air then a measurement of 4 outside air from within the outside air duct 60 going into the supply air handler will provide accurate results for at least gas or VOC measurements. For at least particle measurements, 6 however, the measurement must be taken after the air filters and fan systems such as at a 7 location downstream of them such as the supply duct locations mentioned above. If return air 8 from other areas is mixed with the outside air to produce the supply air, then the use of a 9 downstream supply duct airflow measurement is also necessary with a location at least after 1o where the outside air and return air become well mixed. The use of only one supply or 11 outside air duct measurement should be sufficient for all the spaces fed from a single air .12 handler or main supply duct since all the supply air flowing into these spaces from the same 1.3 air system should have similar characteristics and contaminants.
14 Next each pair of air contaminant measurements (space air and outside or supply air) is turned into a set of differential measurements by subtracting the outside or supply air i6 contaminant measurement from the space air contaminant measurement. An example of an 17 embodiment to perform this is the subtraction block 35 of FIG. 5 where a supply or outside 18 air measurement of for example TVOC's would be applied to the minus (-) input of the 1g subtraction block and the room or room exhaust duct air contaminant measurement of 2o TVOC's would then be applied to the positive (+) input. The output would then be the 21 differential measurement of TVOC's for that space. Other methods of subtracting these air 22 contaminant measurements for software variables in a computerized control system for 23 example or for other implementations would be known to those well skilled in the art.
24 The individual differential air contaminant measurements would then be treated in the same manner described previously for the non-differential room air measurements and thus 26 would be used, for example, individually or combined and then compared or analyzed by 27 signal processing controller block 130, 210, 530 or 420 of FIG 1, 2, 4 or 6 respectively to 28 create signals 31 and 32 that would be used to vary the supply and exhaust airflows of space 29 20.
The air sampling embodiments of FIG. 1 and 2 are preferred embodiments for this 31 differential measurement control concept since the measurement of the supply or outside air 32 and the space air measurement can be performed with the same sensor within a reasonably 33 short period of time such as 5 to 30 minutes. As a result many sensor errors are eliminated 34 since they cancel out when subtracting the two measurements. Consequently, very accurate 1 differential measurements can be made even when the increase in contaminants in the room 2 although important is relatively small compared to a potentially high source level of outside 3 air contaminants. As a result these high outdoor background levels do not substantially 4 decrease the resolution or accuracy of the measurement of the effects of any contaminant sources within the critical environment spaces.
6 Another control approach that can be used with the implementation of FIG. 1, 2 or 6 7 relates to a situation where a high level of supply or outside air contaminant may be present, 8 yet the differential room air signal mentioned previously indicates that there are not 9 substantive sources of contaminants in the space. In this situation the absolute level of 1o contaminants in the space may be high enough to trigger an increased dilution level, but the 11 differential signal correctly indicates that increasing the supply air is not appropriate. In this 12 situation, since the source of the contaminant is the supply air, it may be advantageous to 13 reduce the supply air until the outside or source air contains a lower level of contaminants.
14 One embodiment of this control approach consists of making one or more air contaminant measurements in the supply duct 50B or outside air intake duct 60 as mentioned 16 previously. These one or more contaminant measurements can then be combined or used 17 individually and then compared or analyzed by signal processing controller block 130, 210, 18 530 or 420 of FIG 1, 2, 4 or 6 respectively to determine if these signals exceed appropriate 19 trigger levels such as those used for the critical environment spaces 20.
If these trigger levels or appropriate trigger conditions are met, then blocks 130, 210 or 420 can be used to reduce 21 the supply flow by one of several approaches. For example, in FIG. 3 the temperature control 22 output 93 of the Temperature control block 90 can be completely overridden and effectively 23 disabled by a command output from signal processing controller blocks 130, 210 or 420 so 24 that the supply flow will become controlled by the higher of either just the makeup requirements of the special exhaust devices or the flow commanded by the dilution 26 ventilation command 31 which would be reduced to a low level.
27 Another control approach that can be used with the implementation of FIG.
1, 2 or 6 28 relates to a situation where a high level of contaminants may be present around the room or 29 space of interest particularly from a space such as the corridor which is positive to the room 3o of interest and from which the room's offset airflow is drawn. In this situation, it may be 31 desirable to create a differential signal for each contaminant of interest as was mentioned 32 previously for outside or supply air. In this case, for example, the measured air contaminants 33 from room 20 would be subtracted from the respective air contaminant measurements taken 34 from corridor 10 or from an anteroom, or other space which provides at least a portion of 1 room 20's offset airflow 21. When this differential signal shows a high level it indicates that 2 the source of contaminants detected is in the room 20 not in the corridor 10 or other 3 anteroom. This is important since in the case of someone cleaning the corridor with a 4 cleaning agent that gives off VOC's, these VOC's will be pulled into all the rooms 20A, 20B
and 20C that feed from the corridor 10. As such if the absolute level of contaminants or even 6 the differential level of contaminants vs. outside air or the supply air is high in the rooms 20 7 due to the VOC's from the corridor it would throw all these rooms into a high level of 8 ventilation. Although this may be acceptable, it may also cause problems with airflow 9 capacity due to potentially all the rooms going to a high level of dilution ventilation. To 1o prevent this airflow shortage condition from occurring, the differential level of these rooms i1 can be checked vs the corridor or equivalently the absolute level of the corridor can be 12 checked. Assuming the corridor is positive to the spaces of interest, if either the corridor 1.3 level is high in any of the air contaminants of concern, or the level of the room is high 14 whereas the differential level of the room compared to the corridor if low, then the correct control action may be to increase the level of ventilation in the corridor, but not to increase 16 the level of ventilation in the room or only to partially increase this level to some 17 intermediate level. Another means of implementing this control strategy is to only increase 18 the room 20's dilution ventilation command when both the differential signal of the room to 1.9 the supply (or outside air) is high and the differential signal of the room 20 to the corridor 10 (or other offset airflow source area) is also high.
21 Other strategies that could be implemented when these differential signals and 22 corridor signals indicate the source of contamination is from the corridor 10 are to change the 23 airflow direction to make the rooms positive vs. the corridor. For example there could be a 24 source of smoke, VOC's or other contaminants either in the corridor or from another room that has in turn breached its containment and then contaminated the corridor.
In these 26 situations, the appropriate action could be to use the signal processing controller block 130, 27 210, 530 or 420 of FIG 1, 2, 4 or 6 to sense this condition as mentioned above and then use 28 the room offset airflow control signals 32 to change the room 20's offset airflow 21 from into 29 the rooms to out of the room. This would also require changing the corresponding offset airflow of the corridor from positive to negative so the combination of the rooms 20 and the 31 corridor 10 remains balanced. In some cases the rooms 20 may already be positive to the 32 corridor 10. In this case it may be advantageous to increase the level of positive offset 33 airflow 21 to an even greater value to ensure better protection from the contaminants in the 34 corridor 10. If the contaminant level in one of the rooms is higher than any other room, then 1 that room may likely be the source of the contaminant. If that is the case then the signal 2 processing controller block 130, 210, 530, or 420 of FIG 1, 2, 4, or 6 can be used to modify 3 the offset airflow control signal 32 for that room 20 to make the room offset airflow 21 4 negative and to as high a level as is appropriate, while also modifying the corridor 10 offset 6 airflow to the appropriate level. This concept of balancing offset airflows in a corridor 10 vs.
6 the rooms 20 off from that corridor due to the need to change the offset airflows in a room 20 7 is described in U.S. Patent No. 5,545,086 entitled "Air Flow Control For Pressurized Room 8 Facility".
9 Although specific features of the invention are shown in some drawings and not others, this is for convenience only as soine feature may be combined with any or all of the ii other features in accordance with the invention.
12 Other embodiments will occur to those skilled in the art and are within the following 13 claims:
14 What is claimed is:
|Citing Patent||Filing date||Publication date||Applicant||Title|
|CN104601657A *||12 Dec 2014||6 May 2015||北京拓扑智鑫科技有限公司||Park green ecological index online publishing system and implementation method thereof|
|International Classification||G01F23/00, F24F11/00|
|Cooperative Classification||Y02B30/78, F24F2011/0032, F24F11/0017, F24F2011/0026, F24F11/0012, G01N1/26, Y02B30/767, F24F11/0001, F24F3/0442, G01N33/0063, G01N1/2273, F24F3/044, F24F11/0086, F24F11/0015|
|European Classification||F24F3/044B, F24F11/00R9, F24F3/044, G01N1/26, F24F11/00R3C, F24F11/00C|
|17 Jun 2010||EEER||Examination request|
|17 Jul 2013||FZDE||Dead|
Effective date: 20130522