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Home , Dilution (equation), Humidity, Indoor air quality, Infiltration (HVAC), Refrigerant, Stack effect

Factors Affecting

The indoor environment in any the categories that follow. The examples is a result of the interaction between the given for each category are not intended to site, , building system (original be a complete list. 2 design and later modifications in the Sources Outside Building structure and mechanical systems), con- struction techniques, contaminant sources Contaminated outdoor air (building materials and furnishings, n pollen, dust, fungal spores moisture, processes and activities within the n industrial building, and outdoor sources), and n general exhaust building occupants. Emissions from nearby sources The following four elements are involved n exhaust from on nearby roads Four elements— in the development of indoor air quality or in parking lots, or garages sources, the HVAC n loading docks problems: system, n from dumpsters Source: there is a source of contamination pathways, and or discomfort indoors, outdoors, or within n re-entrained (drawn back into the occupants—are the mechanical systems of the building. building) exhaust from the building itself or from neighboring involved in the HVAC: the HVAC system is not able to n unsanitary debris near the outdoor air development of IAQ control existing air contaminants and ensure intake thermal ( and problems. conditions that are comfortable for most occupants). n n leakage from underground fuel tanks Pathways: one or more pollutant pathways n contaminants from previous uses of the connect the pollutant source to the occu- site (e.g., ) pants and a driving force exists to move n pollutants along the pathway(s). Occupants: building occupants are present. Moisture or standing promoting excess microbial growth It is important to understand the role that n rooftops after rainfall each of these factors may play in order to n crawlspace prevent, investigate, and resolve indoor air quality problems. Equipment HVAC system SOURCES OF INDOOR AIR n dust or dirt in ductwork or other CONTAMINANTS components n microbiological growth in drip pans, Indoor air contaminants can originate , ductwork, coils within the building or be drawn in from n improper use of biocides, sealants, and/ outdoors. If contaminant sources are not or cleaning compounds controlled, IAQ problems can arise, even if n improper venting of the HVAC system is properly designed and products well-maintained. It may be helpful to think n leakage of air pollutant sources as fitting into one of

Factors Affecting Indoor Air Quality 5 Non-HVAC equipment Chemicals released from building n emissions from office equipment (vola- components or furnishings tile organic compounds, ) n volatile organic compounds or n supplies (, toners, ) n inorganic compounds n emissions from shops, labs, cleaning Other Sources processes Accidental events n elevator motors and other mechanical systems n spills of water or other n microbiological growth due to flooding Given our present Activities or to from roofs, piping knowledge, it is Personal activities n fire damage (, PCBs from electrical difficult to relate n smoking equipment, odors) complaints of n cooking Special use areas and mixed use buildings n body specific health n smoking lounges n cosmetic odors n effects to exposures Housekeeping activities n print shops, art rooms to specific pollutant n cleaning materials and procedures n exercise rooms , n emissions from stored supplies or trash n beauty salons especially since the n use of deodorizers and fragrances n preparation areas n airborne dust or dirt (e.g., circulated by significant exposures Redecorating/remodeling/repair activities sweeping and vacuuming) may be to low levels n emissions from new furnishings Maintenance activities of pollutant . n dust and fibers from demolition n in from improp- n odors and volatile organic and inorganic erly maintained cooling towers compounds from paint, caulk, adhesives n airborne dust or dirt n microbiologicals released from demoli- n volatile organic compounds from use of tion or remodeling activities paint, caulk, adhesives, and other products Indoor air often contains a variety of n pesticides from pest control activities contaminants at concentrations that are far n emissions from stored supplies below any standards or guidelines for Building Components and Furnishings occupational exposure. Given our present knowledge, it is difficult to relate com- Locations that produce or collect dust or plaints of specific health effects to expo- fibers sures to specific pollutant concentrations, n textured surfaces such as carpeting, especially since the significant exposures curtains, and other textiles may be to low levels of pollutant mixtures. n open shelving n old or deteriorated furnishings HVAC SYSTEM DESIGN AND n materials containing damaged OPERATION Unsanitary conditions and water damage The HVAC system includes all heating, n microbiological growth on or in soiled cooling, and ventilation equipment serving or water-damaged furnishings a building: or , , n microbiological growth in areas of cooling towers, air handling units, exhaust surface fans, ductwork, filters, steam (or heating n standing water from clogged or poorly water) piping. Most of the HVAC discus- designed drains sion in this document applies both to central n dry traps that allow the passage of HVAC systems and to individual compo- nents used as stand-alone units.

6 Section 2 A properly designed and functioning Radiant may cause people HVAC system: located near very hot or very cold surfaces n provides to be uncomfortable even though the n distributes adequate amounts of outdoor setting and the measured air air to meet ventilation needs of all temperature are within the comfort range. building occupants Buildings with large window areas some- n isolates and removes odors and con- times have acute problems of discomfort taminants through control, due to radiant heat gains and losses, with A number of filtration, and exhaust fans the locations of complaints shifting during the day as the sun angle changes. Large variables, including Thermal Comfort vertical surfaces can also produce a personal activity significant flow of naturally-convecting air, levels, uniformity of A number of variables interact to deter- producing complaints of draftiness. mine whether people are comfortable with temperature, radiant Adding insulation to walls helps to the temperature of the indoor air. The heat gain or loss, and moderate the temperature of interior wall activity level, age, and of each humidity, interact to surfaces. Closing curtains reduces heating person affect the thermal comfort require- determine whether from direct and isolates building ments of that individual. The American occupants from exposure to window people are Society of Heating, Refrigerating, and Air- surfaces (which, lacking insulation, are comfortable with the Conditioning Engineers (ASHRAE) likely to be much hotter or colder than the temperature of the Standard 55-1981 describes the tempera- walls). ture and humidity ranges that are comfort- indoor air. Humidity is a factor in thermal comfort. able for most people engaged in largely Raising relative humidity reduces the sedentary activities. That information is ability to lose heat through and summarized on page 57. The ASHRAE , so that the effect is similar to standard assumes “normal” indoor raising the temperature. Humidity ex- clothing. Added layers of clothing reduce tremes can also create other IAQ problems. the rate of heat loss. Excessively high or low relative Uniformity of temperature is important can produce discomfort, while high relative to comfort. When the heating and cooling humidities can promote the growth of needs of rooms within a single zone and (see Appendix C). change at different rates, rooms that are served by a single thermostat may be at Ventilation to Meet Occupant different . Temperature Needs stratification is a common problem caused by , the tendency of light, warm Most air handling units distribute a blend air to rise and heavier, air to sink. If of outdoor air and recirculated indoor air. air is not properly mixed by the ventilation HVAC designs may also include units that system, the temperature near the ceiling introduce 100% outdoor air or that simply can be several degrees warmer than at transfer air within the building. Uncon- floor level. Even if air is properly mixed, trolled quantities of outdoor air enter uninsulated floors over unheated spaces buildings by through windows, can create discomfort in some climate doors, and gaps in the exterior construc- zones. Large fluctuations of indoor tion. Thermal comfort and ventilation temperature can also occur when controls needs are met by supplying “conditioned” have a wide “dead band” (a temperature air (a blend of outdoor and recirculated air range within which neither heating nor that has been filtered, heated or cooled, and cooling takes place). sometimes humidified or dehumidified).

Factors Affecting Indoor Air Quality 7 Large buildings often have interior system was designed may well have (“core”) spaces in which constant cooling established a lower amount of ventilation is required to compensate for heat gener- (in cubic feet of outdoor air per minute per ated by occupants, equipment, and person) than is currently recommended. lighting, while perimeter rooms may (A table of outdoor air quantities recom- require heating or cooling depending on mended by ASHRAE is reproduced on outdoor conditions. page 136 in Appendix B. Note that other The amount of Two of the most common HVAC important aspects of the standard are not outdoor air designs used in modern public and included in this table.) considered adequate commercial buildings are constant and systems. Con- for proper ventilation Control of Odors and stant volume systems are designed to Contaminants has varied provide a constant and to vary the One technique for controlling odors and substantially over air temperature to meet heating and contaminants is to dilute them with time. The current cooling needs. The percentage of outdoor outdoor air. can work only if guideline issued by air may be held constant, but is often there is a consistent and appropriate flow controlled either manually or automatically ASHRAE is Standard of supply air that mixes effectively with to vary with outdoor temperature and 62-1989. room air. The term “ventilation effi- humidity. Controls may include a mini- ciency” is used to describe the ability of mum setting that should allow the system the ventilation system to distribute supply to meet ventilation guidelines for outdoor air and remove internally generated air quantities under design conditions. pollutants. Researchers are currently Variable air volume (VAV) systems studying ways to measure ventilation condition supply air to a constant tempera- efficiency and interpret the results of those ture and ensure thermal comfort by varying measurements. the airflow to occupied spaces. Most early Another technique for isolating odors VAV systems did not allow control of the and contaminants is to design and operate outdoor air quantity, so that a decreasing the HVAC system so that pressure amount of outdoor air was provided as the relationships between rooms are con- flow of supply air was reduced. Some trolled. This control is accomplished by more recent designs ensure a minimum adjusting the air quantities that are supply of outdoor air with static pressure supplied to and removed from each room. devices in the outdoor air stream. Addi- If more air is supplied to a room than is tional -conserving features such as exhausted, the excess air leaks out of the control or heat recovery are space and the room is said to be under also found in some buildings. positive pressure. If less air is supplied Good quality design, installation, and than is exhausted, air is pulled into the testing and balancing are critically impor- space and the room is said to be under tant to the proper operation of all types negative pressure. of HVAC systems, especially VAV Control of pressure relationships is systems, as are regular inspections and critically important in mixed use buildings maintenance. (See Appendix B for further or buildings with special use areas. discussion of HVAC system types.) Lobbies and buildings in general are often The amount of outdoor air considered designed to operate under positive pressure adequate for proper ventilation has varied to prevent or minimize the infiltration of substantially over time. The current unconditioned air, with its potential to guideline issued by ASHRAE is ASHRAE cause drafts and introduce dust, dirt, and Standard 62-1989. The building code that thermal discomfort. Without proper was in force when your building HVAC operation and maintenance, these pressure

8 Section 2 differences are not likely to remain as The HVAC system is generally the originally designed. predominant pathway and driving force for A third technique is to use local exhaust air movement in buildings. However, all systems (sometimes known as dedicated of a building’s components (walls, ceilings, exhaust ventilation systems) to isolate and floors, penetrations, HVAC equipment, and remove contaminants by maintaining occupants) interact to affect the distribution negative pressure in the area around the of contaminants. contaminant source. Local exhaust can be linked to the operation of a particular piece of equipment (such as a kitchen range) or used to treat an entire room (such as a smoking lounge or custodial closet). Air should be exhausted to the outdoors, not recirculated, from locations which produce significant odors and high concentrations of contaminants (such as copy rooms, bathrooms, kitchens, and beauty salons). Spaces where local exhaust is used must be provided with make-up air and the local exhaust must function in coordination with the rest of the ventilation system. Under some circumstances, it may be acceptable to transfer conditioned air from relatively clean parts of a building to comparatively dirty areas and use it as make-up air for a local exhaust system. Such a transfer can For example, as air moves from supply Chases, crawlspaces, and achieve significant energy savings. other hidden spaces can be registers or diffusers to return air , it Air cleaning and filtration devices both sources and pathways is diverted or obstructed by partitions, designed to control contaminants are found for pollutants. walls, and furnishings, and redirected by as components of HVAC systems (for openings that provide pathways for air example, filter boxes in ductwork) and can movement. On a localized basis, the also be installed as independent units. The movement of people has a major impact on effectiveness of air cleaning depends upon the movement of pollutants. Some of the proper equipment selection, installation, pathways change as doors and windows operation, and maintenance. Caution open and close. It is useful to think of the should be used in evaluating the many new entire building — the rooms and the technological developments in the field of connections (e.g., chases, corridors, air cleaning and filtration. stairways, elevator shafts) between them — as part of the air distribution system. POLLUTANT PATHWAYS AND Natural forces exert an important DRIVING FORCES influence on air movement between zones Airflow patterns in buildings result from and between the building’s interior and the combined action of mechanical exterior. Both the and ventilation systems, human activity, and can overpower a building’s mechanical natural forces. Pressure differentials system and disrupt air circulation and created by these forces move airborne ventilation, especially if the building contaminants from areas of relatively envelope is leaky. higher pressure to areas of relatively lower Stack effect is the pressure driven flow pressure through any available openings. produced by convection (the tendency of

Factors Affecting Indoor Air Quality 9 warm air to rise). The stack effect exists Even when the building as a whole is whenever there is an indoor-outdoor maintained under positive pressure, there is temperature difference and becomes always some location (for example, the stronger as the temperature difference outdoor air intake) that is under negative increases. As heated air escapes from pressure relative to the outdoors. Entry of upper levels of the building, indoor air contaminants may be intermittent, occur- moves from lower to upper floors, and ring only when the wind blows from the replacement outdoor air is drawn into direction of the pollutant source. The The basic principle of openings at the lower levels of buildings. interaction between pollutant pathways and air movement from Stack effect airflow can contami- intermittent or variable driving forces can areas of relatively nants between floors by way of stairwells, lead to a single source causing IAQ higher pressure to elevator shafts, utility chases, or other complaints in areas of the building that are areas of relatively openings. distant from each other and from the lower pressure can Wind effects are transient, creating local source. areas of high pressure (on the windward produce many side) and low pressure (on the leeward BUILDING OCCUPANTS patterns of side) of buildings. Depending on the The term “building occupants” is generally contaminant leakage openings in the building exterior, used in this document to describe people distribution. wind can affect the pressure relationships who spend extended time periods (e.g., a within and between rooms. full workday) in the building. Clients and The basic principle of air movement from visitors are also occupants; they may have areas of relatively higher pressure to areas different tolerances and expectations from of relatively lower pressure can produce those who spend their entire workdays in many patterns of contaminant distribution, the building, and are likely to be more including: sensitive to odors. n local circulation in the room containing Groups that may be particularly suscep- the pollutant source tible to effects of indoor air contaminants n air movement into adjacent spaces that include, but are not limited to: are under lower pressure (Note: Even if n allergic or asthmatic individuals two rooms are both under positive n people with respiratory disease pressure compared to the outdoors, one n people whose immune systems are room is usually at a lower pressure than suppressed due to chemotherapy, the other.) radiation therapy, disease, or other n recirculation of air within the zone causes containing the pollutant source or in n contact lens wearers adjacent zones where return systems overlap Some other groups are particularly n movement from lower to upper levels of vulnerable to exposures of certain the building pollutants or pollutant mixtures. For n air movement into the building through example, people with heart disease may be either infiltration of outdoor air or more affected by exposure at lower levels reentry of exhaust air of monoxide than healthy individuals. Children exposed to environ- Air moves from areas of higher pressure mental have been shown to to areas of lower pressure through any be at higher risk of respiratory illnesses available openings. A small crack or hole and those exposed to dioxide have can admit significant amounts of air if the been shown to be at higher risk from pressure differentials are high enough respiratory infections. (which may be very difficult to assess.)

10 Section 2 Because of varying sensitivity among Some complaints by building occupants people, one individual may react to a are clearly related to the discomfort end of particular IAQ problem while surrounding the spectrum. One of the most common occupants have no ill effects. (Symptoms IAQ complaints is that “there’s a funny that are limited to a single person can also smell in here.” Odors are often associated occur when only one work station receives with a perception of poor air quality, the bulk of the pollutant dose.) In other whether or not they cause symptoms. cases, complaints may be widespread. Environmental stressors such as improper Environmental A single indoor air pollutant or problem lighting, noise, vibration, overcrowding, can trigger different reactions in different ergonomic stressors, and job-related stressors such as people. Some may not be affected at all. psychosocial problems (such as job stress) improper lighting, Information about the types of symptoms can produce symptoms that are similar to noise, vibration, can sometimes lead directly to . those associated with poor air quality. overcrowding, However, symptom information is more The term (SBS) ergonomic stressors, likely to be useful for identifying the timing is sometimes used to describe cases in and job-related and conditions under which problems which building occupants experience acute psychosocial occur. health and comfort effects that are appar- ently linked to the time they spend in the problems (such as job Types of Symptoms and building, but in which no specific illness or stress) can produce Complaints cause can be identified. The complaints symptoms that are may be localized in a particular room or The effects of IAQ problems are often non- similar to those zone or may be widespread throughout the specific symptoms rather than clearly associated with poor building. Many different symptoms have defined illnesses. Symptoms commonly air quality. been associated with SBS, including attributed to IAQ problems include: respiratory complaints, irritation, and n headache . Analysis of air samples often fails n fatigue to detect high concentrations of specific n shortness of breath contaminants. The problem may be caused n sinus congestion by any or all of the following: n cough n the combined effects of multiple n sneezing pollutants at low concentrations n eye, nose, and throat irritation n other environmental stressors n skin irritation (e.g., overheating, poor lighting, noise) n dizziness n ergonomic stressors n nausea n job-related psychosocial stressors All of these symptoms, however, may also (e.g., overcrowding, labor-management be caused by other factors, and are not problems) necessarily due to air quality deficiencies. n unknown factors “Health” and “comfort” are used to Building-related illness (BRI) is a term describe a spectrum of physical sensations. referring to illness brought on by exposure For example, when the air in a room is to the building air, where symptoms of slightly too warm for a person’s activity diagnosable illness are identified (e.g., level, that person may experience mild certain or infections) and can be discomfort. If the temperature continues to directly attributed to environmental agents rise, discomfort increases and symptoms in the air. Legionnaire’s disease and such as fatigue, stuffiness, and headaches hypersensitivity pneumonitis are examples can appear. of BRI that can have serious, even - threatening consequences.

Factors Affecting Indoor Air Quality 11 A small percentage of the population Sometimes several building occupants may be sensitive to a number of chemicals experience rare or serious health problems in indoor air, each of which may occur at (e.g., cancer, miscarriages, Lou Gehrig’s very low concentrations. The existence of disease) over a relatively short time period. this condition, which is known as multiple These clusters of health problems are chemical sensitivity (MCS), is a matter of occasionally blamed on indoor air quality, considerable controversy. MCS is not and can produce tremendous currently recognized by the major medical among building occupants. State or local organizations, but medical opinion is Health Departments can provide advice divided, and further research is needed. and assistance if clusters are suspected. The applicability of access for the disabled They may be able to help answer key and worker’s compensation regulations to questions such as whether the apparent people who believe they are chemically cluster is actually unusual and whether the sensitive may become concerns for facility underlying cause could be related to IAQ. managers.

12 Section 2