IAQ Building Education and Assessment Model (I-BEAM)

1. [SUPPLY AIR] Ventilation air is constantly being supplied to all occupied spaces through the supply air stream. Notice that the supply air is made up of some clean outdoor air and some recirculated air. Recirculated air often makes up the major portion of the supply air stream.
2. [RETURN AIR] Air inside the offices is accumulating pollutants from occupants and their activities and from the building fabric or other indoor sources. Contaminated office air is leaving the offices through the return air vent. Some portion of this contaminated return air exits the building through the “relief air vent”. The remainder is being “recirculated” and “diluted by the outdoor air” entering the air handler from outside.
3. [OUTDOOR AIR] Outdoor air is being drawn into the supply air stream to “dilute indoor pollutants”. The pollution from indoor sources to which occupants are exposed is directly proportional to the strength of the indoor sources, and inversely proportional to the amount outdoor air in the supply air stream. Since occupants and their activities are often the major source of pollution, ventilation standards for indoor air quality provide for a minimum quantity of outdoor air “per person”. This is designed to insure that as pollution sources from occupants increase, outdoor air increases proportionally to insure adequate dilution.
4. [RELIEF VENT] Building atmospheric pressure relative to the atmospheric pressure outside is the force that is always equalizing the flow into the building with the flow out of the building. The relief vent provides a convenient way for flows to equalize.
5. [EXHAUST VENTILATION] The laboratory contaminants are exhausted directly to the outside. Since the laboratory is a significant potential source of toxic pollutants, none of the laboratory air is recirculated. Ideally, an exhaust hood directly above and close to the laboratory chemicals should be used to trap the pollutants into the exhaust stream and prevent any pollutants from contaminating the breathing zone of the laboratory staff.
6. [INDOOR RELATIVE PRESSURE] Pressure relationships between rooms is designated at the bottom of each room. The pressure relationships indoors are being controlled mechanically through supply, return, and exhaust air flows. Since the office is being maintained at a higher pressure relative to the laboratory, air that may sometimes flow through wall cavities or doorways flows “FROM” the offices “TO” the laboratory but not vice versa.
7. [BUILDING PRESSURIZATION–EXFILTRATION] Air always flows from areas of high atmospheric pressure to areas of low atmospheric pressure. If more air is entering than is leaving the building, the atmospheric pressure inside increases relative to the outside, and thus increases the flow of air exiting the building until the incoming and outgoing flows are equal. The converse is also true. Notice how, except for the laboratory, this building is slightly pressurized to insure that the direction of air flow is from the inside to the outside to prevent outdoor pollutants from infiltrating into the building. Where outdoor humidity is a problem, this might not be a good strategy.
8. [LABORATORY DEPRESSURIZATION–INFILTRATION] The exhaust in the laboratory is depressurizing the laboratory relative to the outside and relative to the office areas. That is why air is flowing into the laboratory. Depressurization is insuring that pollutants from the laboratory do not migrate into the office environments.

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1. [OCCUPANCY] As more people are crowded into offices, indoor pollution increases unless outdoor air ventilation is also increased. Notice how pollution levels inside the crowded offices have increased because of overcrowding without adequate ventilation. The risk of disease transmission among occupants also increases because they are close together. Overcrowded office space is not good for occupant health.
2. [OUTDOOR AIR] In order to maintain good indoor air quality, the outdoor air volume must be increased when occupancies increase in order to provide adequate dilution of indoor contaminants. But increasing the outdoor air in hot weather could strain the cooling capacity of the HVAC system, and in cold weather, may call forth additional demand for preheating incoming air to avoid coil freezing. Overcrowded office space is not good for energy efficient building operations.
3. [AIR HANDLING UNIT CAPACITY] More people means additional outdoor air and higher internal heat gains. This could strain the cooling capacity of the HVAC system. Further, more outdoor air in cold weather could result in coil freezing. Building managers should keep a close eye on the actual occupancy of the building relative to the existing outdoor air settings and the HVAC system’s cooling capacity and preheat needs. Overcrowding is not a good idea for HVAC equipment.

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1. [AN AIR HANDLING UNIT (AHU)] The AHU can release dirt, mold, or chemical contaminants into the supply air stream. Dirty filters, filter changes when the fan is operating, dirty coils or drip pans, excess moisture anywhere leading to mold, deteriorating duct insulation, trash or housekeeping/maintenance products in the mechanical room/mixing chamber—these are COMMON EXAMPLES of pollution sources in the AHU. Does this describe your buildings? Good maintenance and cleanliness not only keep the system running well, they also insure that the AHU does not become a source of indoor air pollution. Who suffers from contamination in the AHU?
2. OCCUPIED SPACES: Notice how the contamination in the AHU spreads to every occupied space serviced by the AHU through the supply air stream. If you have health complaints that are widespread – consider whether the AHU or air ducts are contaminated by improper building maintenance or from other causes.

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1. [OUTDOOR AIR] The outdoor air flow was reduced, ostensibly to save energy. As a result, pollutants have built up in the offices. Do you think that this is the only effect? What do you think has happened to the exhaust system?
2. [EXHAUST] Because total air flow out of the building can not exceed air flowing into the building, the air that the exhaust fans are now capable of drawing out of the laboratory is also reduced because the outdoor air dampers are closed. What will happen to the laboratory chemicals?
3. [PRESSURE] Since the pressure differential between the offices and the laboratory are reduced, laboratory chemicals may now migrate throughout the building.
4. [OCCUPIED SPACES] The reduction in outdoor air had multiple effects: It reduced the dilution of contaminants in the offices; reduced exhaust and thereby increased pollution in areas of high pollution loads such as laboratories, toilets, and copy rooms; and reduced pressure differentials between the offices and laboratory, thereby allowing laboratory pollutants to migrate into the office areas. Reducing outdoor air BELOW APPLICABLE STANDARDS is a BAD IDEA.
5. [INFILTRATION] Because outdoor air flow is reduced, the building is no longer slightly pressurized as intended, and is now depressurized. This causes air to infiltrate from the outside into the office area.

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1. [EXHAUST] Exhaust air flow NEEDS TO BE CHECKED PERIODICALLY. Many factors can account for inadequate exhaust flow. Exhaust fans may not be operating properly or the building may become depressurized because of inadequate outdoor air or for other reasons. Notice how contaminants have accumulated in the laboratory when the exhaust does not operate properly.What happens to laboratory pressure?
2. [PRESSURE] When the exhaust air flow was eliminated, the laboratory became positively pressurized from the supply air. Now chemical contaminants are more likely to spill out into the offices.
3. [OUTDOOR AIR] Because less air is being drawn out of the building through the exhaust, the building has a higher atmospheric pressure so that LESS OUTDOOR AIR ENTERS the building. What does this do to the office contaminants?
4. [OFFICE SPACE] Reducing exhaust air flow has had multiple effects in the office area. Laboratory contaminants spill into the office environment from the laboratory through unintended pathways, and outdoor air which once diluted office contaminants is now reduced. Office pollutants in the office area increase and are joined by laboratory chemicals. Exhaust fans and air flow should be checked periodically to make sure they are functioning properly.

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1. [SUPPLY AIR] Supply air to a given space may shut down for different reasons--a mechanical failure, an ill conceived renovation (e.g. a renovation splits an existing room but does not provide for supply and return to each room), or because of VAV pinch down. In a VAV system, the supply air may be reduced because of thermal neutrality (i.e. the room does not require conditioning), but the VAV box should be set with a MINIMUM STOP high enough to provide ADEQUATE OUTDOOR AIR even when demand for conditioning is low. Notice that contaminants in the space with diminished supply are not diluted but rather build up. Occupants with inadequate supply air may suffer both excess pollution exposure and thermal discomfort.

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1. [OUTDOOR AIR] The weather is cool outside. So the economizer is bringing in large quantities of outdoor air to provide “free cooling”. Humidity is also being carefully controlled. How does increased outdoor air effect pollution levels in the building?
2. [OCCUPIED SPACE] The increased outdoor air flow from the economizer provides greater dilution of indoor generated contaminants in occupied spaces. However, indoor concentrations of outdoor contaminants has slightly increased. As suggested in the picture, except in cases where the outdoor air is highly contaminated, the net effect of increasing outdoor air flow is usually to lower indoor air pollution.

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1. [OUTDOOR AIR] The outdoor air is contaminated from nearby pollution sources outside. This is why the LOCATION OF THE OUTDOOR AIR INTAKE relative to local outdoor pollution sources is very important. Alternatively, the ambient air may be heavily contaminated during an air pollution episode. How does the outdoor pollution affect the occupied spaces inside?
2. [OCCUPIED SPACES] Outdoor pollution enters the building through the outdoor air supply and is carried through the supply air ducts to the occupied spaces. It is not diluting indoor sources but is adding to them. Overall pollution levels inside the building are ELEVATED FROM BOTH THE INDOOR AND THE OUTDOOR POLLUTION SOURCES.