The problem of the “sick” building-facts and implications: Identifying and measuring indoor nonbiologic agents

Abstract

American Society of Heating, Refrigeration, and Air-conditioning Engineers Cubic feet per minute Environmental Protection Agency Heating, ventilation, and air conditioning National Institute for Occupational Safety and Health Occupational Safety and Health Administration The energy crisis of the 1970s resulted in modifications in heating, ventilation, and air-conditioning (HVAC) equipment to minimize air-handling costs by limiting the amount of outside air brought into a building. The standard for the amount of outside air per person supplied by HVAC dropped from 20 to 30 cubic feet per minute (CFM) per person to 5 CFM per person. This value was recommended by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) in their Standards 62-73 [1]ASHRAE Standard 62-73. Standard for natural and mechanical ventilation. American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc,, Atlanta, Georgia1977Google Scholar and 62-81.[2]ASHRAE Standard 62-81. Ventilation for acceptable indoor air quality. American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc,, Atlanta, Georgia1981Google ScholarArchitectural practices and decorating styles also changed during this period. Examples include the use of sealed instead of openable windows, extensive use of wall-to-wall carpeting, and expanded use of particle board. Equipment within buildings, particularly nonindustrial buildings, changed during this same period with the introduction of copying machines, laser printers, personal computers, and other electric devices. These changes in the indoor environment were associated with the introduction of contaminants such as volatile organic compounds from carpets, solvents from paints and varnishes, ozone from copying machines, ammonia from blueprint machines, acetic acid from photographic equipment, and formaldehyde from particle boards used for wall paneling and the construction of desks, cabinets, and other furniture.Other important sources of airborne contaminants are the materials used for building maintenance such as cleaning solutions, disinfectants, carpet shampoos, and floor waxes. Routine human activities also introduce chemicals and particulates in the indoor environment. Examples are cigarette smoke, carbon monoxide, carbon dioxide, oxides of nitrogen generated from cooking activities that use natural gas combustion, and bioeffluents released by human metabolism, such as carbon dioxide, methane, ammonia, hydrogen sulfide, acetaldehyde, pyruvic acid, lactic acid, and butyric acid.The significant drop in outside air requirements, together with the introduction or increase in the large number of new sources of airborne contaminants, have contributed to potential problems with indoor air quality. ASHRAE has subsequently modified the ventilation guidelines, published in 1990 in Standard 62-1989, [3]ASHRAE Standard 62-89. Ventilation for acceptable indoor air quality. American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc,, Atlanta, Georgia1990Google Scholar with the flow rate of outdoor air recommended at 15 to 20 CFM per person. The above discussion focused on the indoor sources and their relationship to the activities and equipment that existed inside the buildings. Obviously, indoor air quality can also be influenced by contaminants that are generated outdoors and enter the building through various pathways such as the shell or ″skin” of the building or through fresh air intakes.The National Institute for Occupational Safety and Health (NIOSH) has been asked to perform what is known as health hazard evaluations in the indoor environment. NIOSH has conducted more than 500 of these evaluations in buildings with indoor air quality complaints. The problems were attributed to inadequate ventilation in 53% of the cases, inside contaminations in 15%, and outside contamination in only 10%. About 5% of the problems were attributed to building material contamination and another 5% to microbial contamination.[4]Congressional testimony of J. Donald Millar, Director, before the Subcommittee on Superfund, Ocean, and Water Protection, Committee on Environment and Public Works, U.S. Senate, on May 26, 1989NIOSH indoor air quality, selected references. US Department of Health and Human Services, Centers for Disease Control, 1989Google ScholarTECHNICAL TERMS AND UNITSIn this section some of the important technical terms and units encountered during the evaluation of air quality will be introduced and discussed.CFM of outdoor air per personThis is the unit of air flow specified in ASHRAE Standard 62-1989.[3]ASHRAE Standard 62-89. Ventilation for acceptable indoor air quality. American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc,, Atlanta, Georgia1990Google Scholar It is the air flow rate of outside air delivered to the building divided by the number of persons occupying the space.CFM of outdoor air per square ftThis is another way to specify ventilation rate of outdoor air. It is expressed in net occupiable area and not gross area of the building. This unit is also used in the ASHRAE standard. [3]ASHRAE Standard 62-89. Ventilation for acceptable indoor air quality. American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc,, Atlanta, Georgia1990Google ScholarAir changes per hourThis is the conventional way to express the total actual dilution ventilation rate of a specific space. It is equal to the ventilation air flow rate in CFM divided by the volume of ventilated space in cubic feet. However, it can also be used to express air changes per hour of outdoor air.Concentration of gases and vaporsA gas is a substance that is in the gaseous phase at normal temperature and pressure. A vapor is the gaseous phase of a material that is a solid or a liquid at normal temperature and pressure. The concentration can be expressed in units of parts of contaminant per million parts of air by volume (parts per million) or in weight of contaminant (milligrams) per unit volume of air (cubic meters).Concentration of particulatesConcentration of particles is usually expressed as weight of dust (milligrams) per unit volume of air (cubic meters). Under some circumstances the concentration of dust that can be tolerated is very low, such as in clean rooms used in electronics and the space industry or in the case of asbestos fibers in indoor air. Concentration is expressed in these situations as number of particles or fibers per milliliter of air.INDOOR AIR QUALITY INVESTIGATIONSInvestigations into building complaints should be approached in a systemic fashion similar to that used in industrial hygiene surveys. The first step is to collect and review available documents and records regarding design, construction, floor plans (blueprints), space modifications and remodeling, history of HVAC maintenance, and finally documented complaints by the building's occupants. The next step is a walkthrough survey conducted to search for indicators and sources of air pollutants, such as odors, staining, mold growth, signs of water damage, and sanitation problems. It is also important to inspect the activities in the immediate vicinity of the building to identify other possible causes for the complaints, such as the presence of car parking facilities.Although radon and asbestos are considered the two major indoor air pollutants, short-term health effects are not associated with these two contaminants. The symptoms will most probably be related to biologic and other nonbiologic agents. The main nonbiologic contaminants and their sources are shown in Table I.TABLE IMain nonbiologic contaminants and their sourcesContaminantSourcesAcetic acidPhotographic and x-ray development equipment, and silicone caulking compoundsCarbon dioxideUnvented gas and kerosene appliances, processes producing combustion products, and human respirationCarbon monoxideTobacco smoke, engine exhausts, unvented gas, and kerosene appliancesFormaldehydeOff-gassing from urea formaldehyde foam insulation, plywood, particle board, paneling, carpeting and fabric, glues, and combustion products including tobacco smokeNitrogen oxidesCombustion products from appliances and tobacco smoke, welding, and gas and diesel engine exhaustOzoneCopy machines, laser printers, electrostatic air cleaners, and smogVolatile organicPaint, cleaning compounds, glues, copy machines, silicone caulking compounds material, insecticides, and combustion products including tobacco smoke, carpetingMiscellaneousMicrofilm equipment, window cleaners, acid drain cleaners, blueprint gases including equipment, and outdoor sources ammonia, hydrogen sulfide, sulfur dioxideMan-madeFibrous glass and mineral wool used in thermal insulation and HVAC mineral fibers ducts Open table in a new tab The third step is to conduct comprehensive personal interviews of the occupants. The history of the complaints, the patterns of symptoms, the spatial locations, and the timing of complaints can be of significant help to identify the area of the problem.The final step in this investigation is environmental monitoring. It is conducted either to identify the agent or to measure and evaluate the extent of the problem when the agent is already identified.SAMPLING FOR NONBIOLOGIC AGENTSAir sampling may seem to be the logical response to an indoor air problem. However, measurement of a specific agent may be misleading as well as very expensive. It should be performed when all the investigations previously described are completed and decisions are reached on location of sampling, time of sampling, and appropriate analytic procedure. Subsequent use of the results should also be considered before the samples are taken. For example, the results can be used to relate indoor concentrations to outdoor conditions, to compare concentrations obtained in complaint areas with those collected in which no symptoms are reported, and to compare the results with specific air quality standards.A sufficient amount of the contaminant must be collected during sampling to perform subsequent qualitative and quantitative analytic procedures. The amount collected will be proportional to the airborne concentration, sampling flow rate, and duration of sampling. Air sampling can be performed to obtain either area or personal samples. The selection of the sampling method depends primarily on the airborne contaminant, the purpose of the survey, and subsequent sample analysis. One should ascertain if a particular situation is covered by statutory requirements by a federal, state, or local regulatory agency before any sampling program is undertaken. If the situation is regulated, then the decision to diverge from the official regulatory agency procedure is a major one, because the individual carries the burden of proof to prove the equivalence of the selected unofficial method. Sampling and analytic techniques are described in adequate details in several publications by the Environmental Protection Agency (EPA)* and NIOSH.[5]NIOSH manual of analytical methods. 4th ed. Government Printing Office, Washington, D.C1990Google Scholar Comprehensive descriptions of air sampling equipment are in several recent publications.6ACGIH Air sampling instruments for evaluation of atmospheric contaminants.7th ed. 1989Google Scholar, 73rd ed. Methods of air sampling and analysis. Lewis Publishers, Chelsea, Michigan1989Google Scholar, 8Ness SA Air monitoring for toxic exposure. Van Nostrand Reinhold, New York1991Google Scholar, 9Maslansky CJ Maslansky SP Air monitoring instrumentation. Van Nostrand Reinhold, New York1993Google ScholarAerosol samplingSamples of particles may be collected by various techniques, including filtration, electrostatic precipitation, and impaction. Particle collection can be obtained with or without size separation. Collection without size separation is used to obtain total suspended particulate matter for subsequent gravimetric, chemical, or physical analysis. Collection with size segregation is used for many purposes such as determination of particle size distribution of airborne dust and determination of a specific fraction of the dust cloud that will deposit in the various compartments of the respiratory tract. Examples are the respirable fraction required by the Occupational Safety and Health Administration (OSHA) standards[10]U.S. Department of Labor, Occupational Safety and Health Administration, OSHA safety and health standards (29 CFR 1910, No. 1910.1000).Google Scholar and the mass of particles less than 10 μm fraction required by the EPA's Air Quality Standards.[11]U.S. Code of Federal Regulations. Government Printing Office, Washington, D.C1989Google ScholarSampling of gases and vaporsSampling of gases and vapors can be conducted to obtain grab, intermittent, or continuous samples. Each sampling procedure will provide data representing a range of averaging times. Grab samples can be collected by gas sampling bags, evacuated bottles, gas syringes, and gas detector tubes. Intermittent samples can be obtained by absorbing the gases in liquid media contained in bubblers and impingers or adsorption of gases on solid media such as charcoal and silica gel. A popular new technique is passive dosimetry. Gases and vapors are allowed to diffuse into the collection medium of the dosimeter, and therefore the use of an air moving device such as an air pump is not needed. Another category of detection device is the direct reading instruments that are used extensively in field evaluations. They can be operated intermittently or in a continuous mode to provide real-time sampling and readout. A major disadvantage of these latter types of instruments is their high cost, which limits the number of available sampling units and makes frequent sampling impractical.EVALUATION CRITERIAThe enforcement of OSHA's safety and health standards in the work environment is possible because of the clearcut relationship between industrial processes and concentrations of airborne contaminants. The exposed population is principally healthy adults who are willing to accept the risks associated with the exposure limited to the work day, which is usually 8 hours. This is not the case with indoor air quality problems that occur in the home, office, schools, and public buildings. The exposed population includes all age group from infants to the elderly. In addition, persons with allergies, diseases of the heart and lungs, and other diseases are at potential risk. Hence the development and enforcement of comprehensive indoor air quality standards is much more difficult. OSHA permissible exposure limits,[10]U.S. Department of Labor, Occupational Safety and Health Administration, OSHA safety and health standards (29 CFR 1910, No. 1910.1000).Google Scholar ACGIH threshold limit values,[12]ACGIH 1993-1994, TLV`s for chemical substances and physical agents and biological exposure indices.1993Google Scholar and NIOSH recommended exposure limits[13]NIOSH guide to chemical hazards. U.S. Department of Health and Human Services, CDC, DHHS (NIOSH), 1989Google Scholar are derived from the industrial setting and should not be used as evaluation criteria for indoor air quality. The only standards that seem to be applicable currently are those published by ASHRAE, [3]ASHRAE Standard 62-89. Ventilation for acceptable indoor air quality. American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc,, Atlanta, Georgia1990Google Scholar which are derived from recommendations by the World Health Organization.[14]WHO Indoor air quality research, report on a WHO meeting, Stockholm. World Health Organization, CopenhagenAugust 27-31, 1984Google ScholarBuilding owners and managers concerned about the possibility of indoor air quality problems in their property may consult the ″Guide for building owners and facility managers” published by the EPA and NIOSH.[15]U.S. Environmental Protection Agency Office of Air and Radiation Office of Atmospheric and Indoor Air Programs Indoor Air Division Building Air Quality A guide for building owners and facility managers.1991Google Scholar The energy crisis of the 1970s resulted in modifications in heating, ventilation, and air-conditioning (HVAC) equipment to minimize air-handling costs by limiting the amount of outside air brought into a building. The standard for the amount of outside air per person supplied by HVAC dropped from 20 to 30 cubic feet per minute (CFM) per person to 5 CFM per person. This value was recommended by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) in their Standards 62-73 [1]ASHRAE Standard 62-73. Standard for natural and mechanical ventilation. American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc,, Atlanta, Georgia1977Google Scholar and 62-81.[2]ASHRAE Standard 62-81. Ventilation for acceptable indoor air quality. American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc,, Atlanta, Georgia1981Google Scholar Architectural practices and decorating styles also changed during this period. Examples include the use of sealed instead of openable windows, extensive use of wall-to-wall carpeting, and expanded use of particle board. Equipment within buildings, particularly nonindustrial buildings, changed during this same period with the introduction of copying machines, laser printers, personal computers, and other electric devices. These changes in the indoor environment were associated with the introduction of contaminants such as volatile organic compounds from carpets, solvents from paints and varnishes, ozone from copying machines, ammonia from blueprint machines, acetic acid from photographic equipment, and formaldehyde from particle boards used for wall paneling and the construction of desks, cabinets, and other furniture. Other important sources of airborne contaminants are the materials used for building maintenance such as cleaning solutions, disinfectants, carpet shampoos, and floor waxes. Routine human activities also introduce chemicals and particulates in the indoor environment. Examples are cigarette smoke, carbon monoxide, carbon dioxide, oxides of nitrogen generated from cooking activities that use natural gas combustion, and bioeffluents released by human metabolism, such as carbon dioxide, methane, ammonia, hydrogen sulfide, acetaldehyde, pyruvic acid, lactic acid, and butyric acid. The significant drop in outside air requirements, together with the introduction or increase in the large number of new sources of airborne contaminants, have contributed to potential problems with indoor air quality. ASHRAE has subsequently modified the ventilation guidelines, published in 1990 in Standard 62-1989, [3]ASHRAE Standard 62-89. Ventilation for acceptable indoor air quality. American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc,, Atlanta, Georgia1990Google Scholar with the flow rate of outdoor air recommended at 15 to 20 CFM per person. The above discussion focused on the indoor sources and their relationship to the activities and equipment that existed inside the buildings. Obviously, indoor air quality can also be influenced by contaminants that are generated outdoors and enter the building through various pathways such as the shell or ″skin” of the building or through fresh air intakes. The National Institute for Occupational Safety and Health (NIOSH) has been asked to perform what is known as health hazard evaluations in the indoor environment. NIOSH has conducted more than 500 of these evaluations in buildings with indoor air quality complaints. The problems were attributed to inadequate ventilation in 53% of the cases, inside contaminations in 15%, and outside contamination in only 10%. About 5% of the problems were attributed to building material contamination and another 5% to microbial contamination.[4]Congressional testimony of J. Donald Millar, Director, before the Subcommittee on Superfund, Ocean, and Water Protection, Committee on Environment and Public Works, U.S. Senate, on May 26, 1989NIOSH indoor air quality, selected references. US Department of Health and Human Services, Centers for Disease Control, 1989Google Scholar TECHNICAL TERMS AND UNITSIn this section some of the important technical terms and units encountered during the evaluation of air quality will be introduced and discussed.CFM of outdoor air per personThis is the unit of air flow specified in ASHRAE Standard 62-1989.[3]ASHRAE Standard 62-89. Ventilation for acceptable indoor air quality. American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc,, Atlanta, Georgia1990Google Scholar It is the air flow rate of outside air delivered to the building divided by the number of persons occupying the space.CFM of outdoor air per square ftThis is another way to specify ventilation rate of outdoor air. It is expressed in net occupiable area and not gross area of the building. This unit is also used in the ASHRAE standard. [3]ASHRAE Standard 62-89. Ventilation for acceptable indoor air quality. American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc,, Atlanta, Georgia1990Google ScholarAir changes per hourThis is the conventional way to express the total actual dilution ventilation rate of a specific space. It is equal to the ventilation air flow rate in CFM divided by the volume of ventilated space in cubic feet. However, it can also be used to express air changes per hour of outdoor air.Concentration of gases and vaporsA gas is a substance that is in the gaseous phase at normal temperature and pressure. A vapor is the gaseous phase of a material that is a solid or a liquid at normal temperature and pressure. The concentration can be expressed in units of parts of contaminant per million parts of air by volume (parts per million) or in weight of contaminant (milligrams) per unit volume of air (cubic meters).Concentration of particulatesConcentration of particles is usually expressed as weight of dust (milligrams) per unit volume of air (cubic meters). Under some circumstances the concentration of dust that can be tolerated is very low, such as in clean rooms used in electronics and the space industry or in the case of asbestos fibers in indoor air. Concentration is expressed in these situations as number of particles or fibers per milliliter of air. In this section some of the important technical terms and units encountered during the evaluation of air quality will be introduced and discussed. CFM of outdoor air per personThis is the unit of air flow specified in ASHRAE Standard 62-1989.[3]ASHRAE Standard 62-89. Ventilation for acceptable indoor air quality. American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc,, Atlanta, Georgia1990Google Scholar It is the air flow rate of outside air delivered to the building divided by the number of persons occupying the space. This is the unit of air flow specified in ASHRAE Standard 62-1989.[3]ASHRAE Standard 62-89. Ventilation for acceptable indoor air quality. American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc,, Atlanta, Georgia1990Google Scholar It is the air flow rate of outside air delivered to the building divided by the number of persons occupying the space. CFM of outdoor air per square ftThis is another way to specify ventilation rate of outdoor air. It is expressed in net occupiable area and not gross area of the building. This unit is also used in the ASHRAE standard. [3]ASHRAE Standard 62-89. Ventilation for acceptable indoor air quality. American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc,, Atlanta, Georgia1990Google Scholar This is another way to specify ventilation rate of outdoor air. It is expressed in net occupiable area and not gross area of the building. This unit is also used in the ASHRAE standard. [3]ASHRAE Standard 62-89. Ventilation for acceptable indoor air quality. American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc,, Atlanta, Georgia1990Google Scholar Air changes per hourThis is the conventional way to express the total actual dilution ventilation rate of a specific space. It is equal to the ventilation air flow rate in CFM divided by the volume of ventilated space in cubic feet. However, it can also be used to express air changes per hour of outdoor air. This is the conventional way to express the total actual dilution ventilation rate of a specific space. It is equal to the ventilation air flow rate in CFM divided by the volume of ventilated space in cubic feet. However, it can also be used to express air changes per hour of outdoor air. Concentration of gases and vaporsA gas is a substance that is in the gaseous phase at normal temperature and pressure. A vapor is the gaseous phase of a material that is a solid or a liquid at normal temperature and pressure. The concentration can be expressed in units of parts of contaminant per million parts of air by volume (parts per million) or in weight of contaminant (milligrams) per unit volume of air (cubic meters). A gas is a substance that is in the gaseous phase at normal temperature and pressure. A vapor is the gaseous phase of a material that is a solid or a liquid at normal temperature and pressure. The concentration can be expressed in units of parts of contaminant per million parts of air by volume (parts per million) or in weight of contaminant (milligrams) per unit volume of air (cubic meters). Concentration of particulatesConcentration of particles is usually expressed as weight of dust (milligrams) per unit volume of air (cubic meters). Under some circumstances the concentration of dust that can be tolerated is very low, such as in clean rooms used in electronics and the space industry or in the case of asbestos fibers in indoor air. Concentration is expressed in these situations as number of particles or fibers per milliliter of air. Concentration of particles is usually expressed as weight of dust (milligrams) per unit volume of air (cubic meters). Under some circumstances the concentration of dust that can be tolerated is very low, such as in clean rooms used in electronics and the space industry or in the case of asbestos fibers in indoor air. Concentration is expressed in these situations as number of particles or fibers per milliliter of air. INDOOR AIR QUALITY INVESTIGATIONSInvestigations into building complaints should be approached in a systemic fashion similar to that used in industrial hygiene surveys. The first step is to collect and review available documents and records regarding design, construction, floor plans (blueprints), space modifications and remodeling, history of HVAC maintenance, and finally documented complaints by the building's occupants. The next step is a walkthrough survey conducted to search for indicators and sources of air pollutants, such as odors, staining, mold growth, signs of water damage, and sanitation problems. It is also important to inspect the activities in the immediate vicinity of the building to identify other possible causes for the complaints, such as the presence of car parking facilities.Although radon and asbestos are considered the two major indoor air pollutants, short-term health effects are not associated with these two contaminants. The symptoms will most probably be related to biologic and other nonbiologic agents. The main nonbiologic contaminants and their sources are shown in Table I.TABLE IMain nonbiologic contaminants and their sourcesContaminantSourcesAcetic acidPhotographic and x-ray development equipment, and silicone caulking compoundsCarbon dioxideUnvented gas and kerosene appliances, processes producing combustion products, and human respirationCarbon monoxideTobacco smoke, engine exhausts, unvented gas, and kerosene appliancesFormaldehydeOff-gassing from urea formaldehyde foam insulation, plywood, particle board, paneling, carpeting and fabric, glues, and combustion products including tobacco smokeNitrogen oxidesCombustion products from appliances and tobacco smoke, welding, and gas and diesel engine exhaustOzoneCopy machines, laser printers, electrostatic air cleaners, and smogVolatile organicPaint, cleaning compounds, glues, copy machines, silicone caulking compounds material, insecticides, and combustion products including tobacco smoke, carpetingMiscellaneousMicrofilm equipment, window cleaners, acid drain cleaners, blueprint gases including equipment, and outdoor sources ammonia, hydrogen sulfide, sulfur dioxideMan-madeFibrous glass and mineral wool used in thermal insulation and HVAC mineral fibers ducts Open table in a new tab The third step is to conduct comprehensive personal interviews of the occupants. The history of the complaints, the patterns of symptoms, the spatial locations, and the timing of complaints can be of significant help to identify the area of the problem.The final step in this investigation is environmental monitoring. It is conducted either to identify the agent or to measure and evaluate the extent of the problem when the agent is already identified. Investigations into building complaints should be approached in a systemic fashion similar to that used in industrial hygiene surveys. The first step is to collect and review available documents and records regarding design, construction, floor plans (blueprints), space modifications and remodeling, history of HVAC maintenance, and finally documented complaints by the building's occupants. The next step is a walkthrough survey conducted to search for indicators and sources of air pollutants, such as odors, staining, mold growth, signs of water damage, and sanitation problems. It is also important to inspect the activities in the immediate vicinity of the building to identify other possible causes for the complaints, such as the presence of car parking facilities. Although radon and asbestos are considered the two major indoor air pollutants, short-term health effects are not associated with these two contaminants. The symptoms will most probably be related to biologic and other nonbiologic agents. The main nonbiologic contaminants and their sources are shown in Table I. The third step is to conduct comprehensive personal interviews of the occupants. The history of the complaints, the patterns of symptoms, the spatial locations, and the timing of complaints can be of significant help to identify the area of the problem. The final step in this investigation is environmental monitoring. It is conducted either to identify the agent or to measure and evaluate the extent of the problem when the agent is already identified. SAMPLING FOR NONBIOLOGIC AGENTSAir sampling may seem to be the logical response to an indoor air problem. However, measurement of a specific agent may be misleading as well as very expensive. It should be performed when all the investigations previously described are completed and decisions are reached on location of sampling, time of sampling, and appropriate analytic procedure. Subsequent use of the results should also be considered before the samples are taken. For example, the results can be used to relate indoor concentrations to outdoor conditions, to compare concentrations obtained in complaint areas with those collected in which no symptoms are reported, and to compare the results with specific air quality standards.A sufficient amount of the contaminant must be collected during sampling to perform subsequent qualitative and quantitative analytic procedures. The amount collected will be proportional to the airborne concentration, sampling flow rate, and duration of sampling. Air sampling can be performed to obtain either area or personal samples. The selection of the sampling method depends primarily on the airborne contaminant, the purpose of the survey, and subsequent sample analysis. One should ascertain if a particular situation is covered by statutory requirements by a federal, state, or local regulatory agency before any sampling program is undertaken. If the situation is regulated, then the decision to diverge from the official regulatory agency procedure is a major one, because the individual carries the burden of proof to prove the equivalence of the selected unofficial method. Sampling and analytic techniques are described in adequate details in several publications by the Environmental Protection Agency (EPA)* and NIOSH.[5]NIOSH manual of analytical methods. 4th ed. Government Printing Office, Washington, D.C1990Google Scholar Comprehensive descriptions of air sampling equipment are in several recent publications.6ACGIH Air sampling instruments for evaluation of atmospheric contaminants.7th ed. 1989Google Scholar, 73rd ed. Methods of air sampling and analysis. Lewis Publishers, Chelsea, Michigan1989Google Scholar, 8Ness SA Air monitoring for toxic exposure. Van Nostrand Reinhold, New York1991Google Scholar, 9Maslansky CJ Maslansky SP Air monitoring instrumentation. Van Nostrand Reinhold, New York1993Google ScholarAerosol samplingSamples of particles may be collected by various techniques, including filtration, electrostatic precipitation, and impaction. Particle collection can be obtained with or without size separation. Collection without size separation is used to obtain total suspended particulate matter for subsequent gravimetric, chemical, or physical analysis. Collection with size segregation is used for many purposes such as determination of particle size distribution of airborne dust and determination of a specific fraction of the dust cloud that will deposit in the various compartments of the respiratory tract. Examples are the respirable fraction required by the Occupational Safety and Health Administration (OSHA) standards[10]U.S. Department of Labor, Occupational Safety and Health Administration, OSHA safety and health standards (29 CFR 1910, No. 1910.1000).Google Scholar and the mass of particles less than 10 μm fraction required by the EPA's Air Quality Standards.[11]U.S. Code of Federal Regulations. Government Printing Office, Washington, D.C1989Google ScholarSampling of gases and vaporsSampling of gases and vapors can be conducted to obtain grab, intermittent, or continuous samples. Each sampling procedure will provide data representing a range of averaging times. Grab samples can be collected by gas sampling bags, evacuated bottles, gas syringes, and gas detector tubes. Intermittent samples can be obtained by absorbing the gases in liquid media contained in bubblers and impingers or adsorption of gases on solid media such as charcoal and silica gel. A popular new technique is passive dosimetry. Gases and vapors are allowed to diffuse into the collection medium of the dosimeter, and therefore the use of an air moving device such as an air pump is not needed. Another category of detection device is the direct reading instruments that are used extensively in field evaluations. They can be operated intermittently or in a continuous mode to provide real-time sampling and readout. A major disadvantage of these latter types of instruments is their high cost, which limits the number of available sampling units and makes frequent sampling impractical. Air sampling may seem to be the logical response to an indoor air problem. However, measurement of a specific agent may be misleading as well as very expensive. It should be performed when all the investigations previously described are completed and decisions are reached on location of sampling, time of sampling, and appropriate analytic procedure. Subsequent use of the results should also be considered before the samples are taken. For example, the results can be used to relate indoor concentrations to outdoor conditions, to compare concentrations obtained in complaint areas with those collected in which no symptoms are reported, and to compare the results with specific air quality standards. A sufficient amount of the contaminant must be collected during sampling to perform subsequent qualitative and quantitative analytic procedures. The amount collected will be proportional to the airborne concentration, sampling flow rate, and duration of sampling. Air sampling can be performed to obtain either area or personal samples. The selection of the sampling method depends primarily on the airborne contaminant, the purpose of the survey, and subsequent sample analysis. One should ascertain if a particular situation is covered by statutory requirements by a federal, state, or local regulatory agency before any sampling program is undertaken. If the situation is regulated, then the decision to diverge from the official regulatory agency procedure is a major one, because the individual carries the burden of proof to prove the equivalence of the selected unofficial method. Sampling and analytic techniques are described in adequate details in several publications by the Environmental Protection Agency (EPA)* and NIOSH.[5]NIOSH manual of analytical methods. 4th ed. Government Printing Office, Washington, D.C1990Google Scholar Comprehensive descriptions of air sampling equipment are in several recent publications.6ACGIH Air sampling instruments for evaluation of atmospheric contaminants.7th ed. 1989Google Scholar, 73rd ed. Methods of air sampling and analysis. Lewis Publishers, Chelsea, Michigan1989Google Scholar, 8Ness SA Air monitoring for toxic exposure. Van Nostrand Reinhold, New York1991Google Scholar, 9Maslansky CJ Maslansky SP Air monitoring instrumentation. Van Nostrand Reinhold, New York1993Google Scholar Aerosol samplingSamples of particles may be collected by various techniques, including filtration, electrostatic precipitation, and impaction. Particle collection can be obtained with or without size separation. Collection without size separation is used to obtain total suspended particulate matter for subsequent gravimetric, chemical, or physical analysis. Collection with size segregation is used for many purposes such as determination of particle size distribution of airborne dust and determination of a specific fraction of the dust cloud that will deposit in the various compartments of the respiratory tract. Examples are the respirable fraction required by the Occupational Safety and Health Administration (OSHA) standards[10]U.S. Department of Labor, Occupational Safety and Health Administration, OSHA safety and health standards (29 CFR 1910, No. 1910.1000).Google Scholar and the mass of particles less than 10 μm fraction required by the EPA's Air Quality Standards.[11]U.S. Code of Federal Regulations. Government Printing Office, Washington, D.C1989Google Scholar Samples of particles may be collected by various techniques, including filtration, electrostatic precipitation, and impaction. Particle collection can be obtained with or without size separation. Collection without size separation is used to obtain total suspended particulate matter for subsequent gravimetric, chemical, or physical analysis. Collection with size segregation is used for many purposes such as determination of particle size distribution of airborne dust and determination of a specific fraction of the dust cloud that will deposit in the various compartments of the respiratory tract. Examples are the respirable fraction required by the Occupational Safety and Health Administration (OSHA) standards[10]U.S. Department of Labor, Occupational Safety and Health Administration, OSHA safety and health standards (29 CFR 1910, No. 1910.1000).Google Scholar and the mass of particles less than 10 μm fraction required by the EPA's Air Quality Standards.[11]U.S. Code of Federal Regulations. Government Printing Office, Washington, D.C1989Google Scholar Sampling of gases and vaporsSampling of gases and vapors can be conducted to obtain grab, intermittent, or continuous samples. Each sampling procedure will provide data representing a range of averaging times. Grab samples can be collected by gas sampling bags, evacuated bottles, gas syringes, and gas detector tubes. Intermittent samples can be obtained by absorbing the gases in liquid media contained in bubblers and impingers or adsorption of gases on solid media such as charcoal and silica gel. A popular new technique is passive dosimetry. Gases and vapors are allowed to diffuse into the collection medium of the dosimeter, and therefore the use of an air moving device such as an air pump is not needed. Another category of detection device is the direct reading instruments that are used extensively in field evaluations. They can be operated intermittently or in a continuous mode to provide real-time sampling and readout. A major disadvantage of these latter types of instruments is their high cost, which limits the number of available sampling units and makes frequent sampling impractical. Sampling of gases and vapors can be conducted to obtain grab, intermittent, or continuous samples. Each sampling procedure will provide data representing a range of averaging times. Grab samples can be collected by gas sampling bags, evacuated bottles, gas syringes, and gas detector tubes. Intermittent samples can be obtained by absorbing the gases in liquid media contained in bubblers and impingers or adsorption of gases on solid media such as charcoal and silica gel. A popular new technique is passive dosimetry. Gases and vapors are allowed to diffuse into the collection medium of the dosimeter, and therefore the use of an air moving device such as an air pump is not needed. Another category of detection device is the direct reading instruments that are used extensively in field evaluations. They can be operated intermittently or in a continuous mode to provide real-time sampling and readout. A major disadvantage of these latter types of instruments is their high cost, which limits the number of available sampling units and makes frequent sampling impractical. EVALUATION CRITERIAThe enforcement of OSHA's safety and health standards in the work environment is possible because of the clearcut relationship between industrial processes and concentrations of airborne contaminants. The exposed population is principally healthy adults who are willing to accept the risks associated with the exposure limited to the work day, which is usually 8 hours. This is not the case with indoor air quality problems that occur in the home, office, schools, and public buildings. The exposed population includes all age group from infants to the elderly. In addition, persons with allergies, diseases of the heart and lungs, and other diseases are at potential risk. Hence the development and enforcement of comprehensive indoor air quality standards is much more difficult. OSHA permissible exposure limits,[10]U.S. Department of Labor, Occupational Safety and Health Administration, OSHA safety and health standards (29 CFR 1910, No. 1910.1000).Google Scholar ACGIH threshold limit values,[12]ACGIH 1993-1994, TLV`s for chemical substances and physical agents and biological exposure indices.1993Google Scholar and NIOSH recommended exposure limits[13]NIOSH guide to chemical hazards. U.S. Department of Health and Human Services, CDC, DHHS (NIOSH), 1989Google Scholar are derived from the industrial setting and should not be used as evaluation criteria for indoor air quality. The only standards that seem to be applicable currently are those published by ASHRAE, [3]ASHRAE Standard 62-89. Ventilation for acceptable indoor air quality. American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc,, Atlanta, Georgia1990Google Scholar which are derived from recommendations by the World Health Organization.[14]WHO Indoor air quality research, report on a WHO meeting, Stockholm. World Health Organization, CopenhagenAugust 27-31, 1984Google ScholarBuilding owners and managers concerned about the possibility of indoor air quality problems in their property may consult the ″Guide for building owners and facility managers” published by the EPA and NIOSH.[15]U.S. Environmental Protection Agency Office of Air and Radiation Office of Atmospheric and Indoor Air Programs Indoor Air Division Building Air Quality A guide for building owners and facility managers.1991Google Scholar The enforcement of OSHA's safety and health standards in the work environment is possible because of the clearcut relationship between industrial processes and concentrations of airborne contaminants. The exposed population is principally healthy adults who are willing to accept the risks associated with the exposure limited to the work day, which is usually 8 hours. This is not the case with indoor air quality problems that occur in the home, office, schools, and public buildings. The exposed population includes all age group from infants to the elderly. In addition, persons with allergies, diseases of the heart and lungs, and other diseases are at potential risk. Hence the development and enforcement of comprehensive indoor air quality standards is much more difficult. OSHA permissible exposure limits,[10]U.S. Department of Labor, Occupational Safety and Health Administration, OSHA safety and health standards (29 CFR 1910, No. 1910.1000).Google Scholar ACGIH threshold limit values,[12]ACGIH 1993-1994, TLV`s for chemical substances and physical agents and biological exposure indices.1993Google Scholar and NIOSH recommended exposure limits[13]NIOSH guide to chemical hazards. U.S. Department of Health and Human Services, CDC, DHHS (NIOSH), 1989Google Scholar are derived from the industrial setting and should not be used as evaluation criteria for indoor air quality. The only standards that seem to be applicable currently are those published by ASHRAE, [3]ASHRAE Standard 62-89. Ventilation for acceptable indoor air quality. American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc,, Atlanta, Georgia1990Google Scholar which are derived from recommendations by the World Health Organization.[14]WHO Indoor air quality research, report on a WHO meeting, Stockholm. World Health Organization, CopenhagenAugust 27-31, 1984Google Scholar Building owners and managers concerned about the possibility of indoor air quality problems in their property may consult the ″Guide for building owners and facility managers” published by the EPA and NIOSH.[15]U.S. Environmental Protection Agency Office of Air and Radiation Office of Atmospheric and Indoor Air Programs Indoor Air Division Building Air Quality A guide for building owners and facility managers.1991Google Scholar