Indoor air quality investigation protocols.

Introduction

The importance of indoor air quality (IAQ) from an environmental health perspective has become evident, especially due to the fact that most people in the United States spend an average of 90% of their time indoors (1). Over the last 10 to 15 years, an increasing number of complaints about discomfort and health effects related to IAQ have been reported. These complaints have come from all types of indoor environments including residential, occupational, and institutional settings. Much of the emphasis has been on office environments and various studies have shown that approximately 20 to 30% of office buildings have widespread IAQ problems (2,3). In response, the U.S. Department of Labor, Occupational Safety and Health Administration (OSHA) proposed an IAQ standard. However, OSHA's hearings on the proposed standard were masked by a flood of testimony on environmental tobacco smoke. As a result, the proposed standard has been put on hold. Regardless, the underlying factors of IAQ still exist and several states have passed IAQ regulations of their own. In the meantime, requests for IAQ investigations have increased with National Institute of Occupational Safety and Health (NIOSH), receiving as many as 3000 calls regarding IAQ in a single week (with 90% requesting an IAQ investigation) (4).

A wide-range of individuals from environmental health professionals to building managers may become involved with investigating IAQ complaints and, as a result, a variety of approaches are taken in performing IAQ investigations. Often IAQ surveys conclude with a list of items not found to be a problem, but with no definitive answer as to the source of the complaints. Two articles have provided brief reviews of IAQ investigation protocols. Light and Presant assessed several survey tools, and Quinlan et al., outlined the NIOSH and the Ontario Ministry of Labour (MOL) protocols, discussing the problems of environmental monitoring in IAQ complaint investigations (5,6). The present paper is a more extensive assessment of IAQ investigation protocols and presents an overview of these protocols along with their strengths and weaknesses. Although these protocols concentrate on office settings, the same approaches can be used for any type of IAQ investigation.

Methods

The information presented in this paper was compiled from searching computerized databases, conducting manual searches of journals and conference proceedings, and by soliciting individuals who are active in the IAQ arena. A literature search was performed of several computerized data bases including: Lexis/Nexis, University of Georgia's library computer database, Environmental Abstracts, and OSHA. This search was supplemented by manual searches of a wide range of environmental health related journals; conference proceedings from organizations such as American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE); books on IAQ; and publication listings from a variety of professional organizations. As a result of these efforts, many articles were retrieved and additional publications were identified. Since IAQ investigations often are very applied work, the findings may go unpublished in traditional refereed journals. In an attempt to supplement the findings from the literature, individuals involved with IAQ within governmental agencies, consulting firms, and private industry were contacted via telephone (and in some cases subsequently by written communication) to solicit IAQ protocol information. With all sources, efforts were focused on identifying and obtaining written IAQ protocols. Once the protocols were secured, each was assessed for approach, content, and usefulness.

Results

The investigation found 15 written IAQ protocols from published sources. Another four protocols were found discussed in a book chapter (7). Unsuccessful attempts were made to obtain the original versions of these four protocols. They included the Public Works Canada (PWC) protocol, the Environmental Health and Engineering (EH&E) protocol, the Danish Building Research Institute (DBRI) protocol, and the Nordic Ventilation Group protocol. The PWC IAQ protocol is very similar to the solution-oriented protocols discussed later. The EH&E protocol was developed and is used by a consulting firm, and the DBRI and Nordic Ventilation Group protocols appear very similar to the epidemiological protocols discussed later. Of the 15 protocols obtained, 13 were evaluated and are discussed in detail in the remainder of this article. Two of the 15 protocols had a very narrow scope and were not deemed suitable for inclusion in this study (8,9). All protocols were published after 1984 and 12 of the 15 were published after 1989. There are many similarities between protocols, [TABULAR DATA FOR TABLE 1 OMITTED] which is not surprising because several authors are contributors to multiple protocols. For example, Bosman (10) and Quinlan (6) are members of the American Industrial Hygienist Association's (AIHA) Technical Committee on Indoor Air Quality and contributed to AIHA's protocol (11). Morey (12) is a member of the American Conference of Governmental Industrial Hygienist's (ACGIH) Committee on Bioaerosols and participated with its protocol (13). Light (5) contributed to the Environmental Protection Agency's (EPA) and NIOSH's Building Air Quality publication (14), while Hansen (15), Rajhans (16), and Woods (12) were members of the review committee for this document. The 13 IAQ investigation protocols were divided into four categories (see Table 1): Solution-oriented; Building Diagnostics; Industrial Hygiene; and Epidemiology. These categories were established in several ways. On the whole, the protocols labeled themselves (10,12,14,15,17-20) or the source of the protocol was the determining factor (11,13,18); while others were categorized based on their similarity in approach (5,6,16).

Solution-oriented

The solution-oriented approach is the most common approach, and eight of the protocols are categorized in this area. This approach "systematically excludes a continually narrowing range of possibilities." That is, one tries to eliminate and narrow-down the range of possible causes for IAQ problems through a step-by-step assessment approach (14). The NIOSH document, "Guidance for Indoor Air Quality Investigations," basically sets the foundation for the subsequent solution-oriented approach protocols to build upon or emulate (17). This approach generally consists of four stages or steps which are summarized in Table 2. It is important to note that if likely causes are identified at any stage, corrective action and mitigation measures can be implemented at that time. Otherwise, the interpretation and analysis of the previous stage(s) leads the investigation.

Building Diagnostics

The building diagnostics approach category consists of two protocols, which are nearly identical. In fact, Woods co-authored both protocols (10,12). Building diagnostics is a new discipline used to identify and recommend solutions for buildings with indoor air problems and also provide reasonable assurance that buildings are not being compromised (10). In this approach, "a skilled expert draws on available knowledge, techniques, and instruments in order to predict a buildings' likely performance over a period of time" (12). Building diagnostics consists of four essential components: (1) knowledge of what to measure; (2) availability of appropriate instrumentation; (3) expertise in interpreting results of measurements; and (4) capability of predicting building performance. Building diagnostics performed on problem buildings seeks to maximize the true-positive outcome and minimize the false-negative outcome. Table 3 summarizes the three-stage building diagnostics [TABULAR DATA FOR TABLE 2 OMITTED] [TABULAR DATA FOR TABLE 3 OMITTED] approach to IAQ investigations.

Industrial Hygiene

Primarily based on their sources (i.e., two industrial hygiene professional organizations), two protocols are categorized as the industrial hygiene approach (11,13). The AIHA Technical Committee on Indoor Environmental Quality has attempted to develop a uniform approach for the investigation of IAQ problems and Table 4 provides an overview of the AIHA protocol. The ACGIH protocol's main focus is on the investigation of building-related complaints associated exclusively with bioaerosols (13). Table 5 provides a summary of the approach suggested by ACGIH.

Epidemiology

The epidemiological approach to IAQ attempts to identify the cause of an IAQ problem by systematically observing the patterns of occurrence of the disease by time, place, and person. From these observations, hypotheses are constructed and tested. Although several of the protocols use epidemiology in their approach, only one protocol is actually defined as an epidemiological protocol (18). Table 6 summarizes the major steps in an epidemiological IAQ investigation.

Discussion

Since 1984, there have been various protocols published for the investigation of IAQ complaints (Table 1). The ultimate goal of the majority of these protocols is to develop a uniform approach that uses consistent terminology in addressing IAQ complaints (11,14-16,19,20). Regardless of the specific protocol, all have similar approaches. Most protocols [TABULAR DATA FOR TABLE 4 OMITTED] begin with general observations, proceed to collect more specific data, and end with conclusions and recommendations. Table 7 provides a generic protocol that summarizes the basic steps of the IAQ investigation protocols and the most common components of each stage.

Although all the protocols have many similarities, there are several areas where there is a wide variation in how something is approached or if an aspect is addressed at all in the given protocol. The differences include the level of importance placed on the evaluation of ventilation systems; the use of questionnaires, interviews, and diaries; and the use of medical and epidemiological data. Additionally, the protocols were found to lack verification procedures and IAQ measurement standards. All these issues are further discussed below.

Disciplines Involved

Several environmental health related disciplines have played major roles in IAQ activities, including industrial hygiene, epidemiology, engineering, and health care providers. However, no single discipline appears to have all the skills required to fully address IAQ complaints and, if used alone, is often inadequate for resolving IAQ problems. In fact, many IAQ investigations fail to reach meaningful conclusions because investigators are either too narrow in their professional training or lack practical experience in building operations (5). Many of the protocols emphasize a multi-disciplinary or combined approach (5,6,10-13,16,18). Baker recognized that the diversity and persistence of IAQ issues suggests that the etiology of health problems is multifactorial, and that effective solutions require a team approach (18). Hence, the tools of the epidemiologist should complement the activities of the industrial hygienist and ventilation engineer (18).

Thus, to successfully resolve IAQ issues, a combined approach that collectively employs the principles of the several relevant disciplines should be used and incorporated into any standardized IAQ protocol. A well-rounded team of investigators should include members with expertise in medicine, industrial hygiene, epidemiology, microbiology, ventilation (engineering), public health, and building maintenance (6). While not necessarily a specific discipline, the addition of in-house personnel (building managers, management, maintenance, etc.) on the IAQ investigation team is also highly recommended (5,10,12,13,14,19).

Ventilation System Inspection

An understanding of the heating ventilation and air conditioning (HVAC) system and operation should be an essential step in all IAQ investigations. Except for Baker's protocol, the ventilation system is extensively and explicitly addressed in every protocol (18). For many IAQ problems, the ventilation system is directly or indirectly the cause (21-24). Specifically, a multitude of epidemiological studies have found that symptoms of sick building syndrome are associated with mechanical ventilation. Inadequate ventilation is implicated as one of the several factors in this association. Inadequate ventilation results in the failure to dilute pollutants generated and emitted indoors (e.g., formaldehyde). The ventilation system itself may also be a source of pollutants (e.g., dirty filters and moisture accumulation) (2). [TABULAR DATA FOR TABLE 5 OMITTED] Furthermore, NIOSH has identified as a common problem the fact that the complexity of the ventilation control system may often be beyond the comprehension of the building operators (3). In general, a survey of the ventilation system begins with a qualitative visual inspection followed by a quantitative evaluation. The qualitative aspects include review of any written material (drawings, equipment descriptions) and information on the system's design and balancing. This activity is followed by discussion with building engineers or maintenance personnel regarding the system. The major components of the HVAC are then inspected and quantitative measurements of air flow and room change rates are used in follow-up as needed.

Measurement Standards

The lack of generally-accepted IAQ standards leads to difficulties that plague all of the current IAQ protocols. At present, all occupational exposure limits are set for the industrial workplace. These levels may have little relevance in the non-industrial workplace, where the main concern may be comfort and a more diverse population may be exposed (6). The current guidelines are not intended for non-industrial settings where contaminant concentrations are often several orders of magnitude less than those found in industrial settings and where a non-working population may be exposed (25). However, the concept of setting limits for non-industrial settings at one-tenth of the industrial level has been used in IAQ investigations (16). Applying a safety factor to occupational guidelines to account for multiple exposure has also been suggested by AIHA. Moreover, the EPA's National Ambient Air Quality Standards (NAAQS), designed to protect the public over an entire day, have been utilized (11,12,15). Woods et al., incorporate odor recognition thresholds in their performance standards (12).

Additionally, there are no established standards for safe levels of airborne microorganisms. In the past, several tentative levels have been recommended: Morey proposed a value of 1000 CFU/[m.sup.3] (22); Gammage recommended a value of 500 CFU/[m.sup.3] above the level in the outside air concentration (8); and the ACGIH recommended sampling both the complaint and control areas for comparison (13).

ASHRAE has established several guidelines for evaluating ventilation systems. Its Standard 62-1989 "Ventilation for Acceptable Indoor Air Quality," while presently being revised, was developed specifically for the indoor environment (26). This standard was approved by the American National Standards Institute (ANSI), and has been adopted by a majority of the building code authorities and IAQ protocols (6,10-12,15,17,19,20). It has commonly been used as a guideline in office building evaluations and for assessing the performance of ventilation systems. The standard was developed to provide acceptable IAQ to building occupants and prevent adverse health effects among them. The standard was designed to satisfy 80 percent of building occupants in indoor environments where a moderate amount of smoking is allowed. There are two different recommended approaches for reaching this goal. The ventilation rate procedure specifies the quality and amount of outdoor air that should be delivered to indoor spaces to reasonably control, through dilution, particulates, odors, and other contaminants. The alternative procedure, known as the IAQ procedure, lists recommended levels for carbon dioxide, chlordane, ozone, and radon progeny, but does not specify ventilation rates to achieve these levels (26). The revised version of ASHRAE's IAQ standard is expected sometime in 1996. ASHRAE's Standard 55-1981 and the revised ASHRAE 551992, "Thermal Environmental Conditions for Human Occupancy," is also widely used for temperature and humidity ranges (6,11,12,14,15,17,19,20).

Furthermore, very little attention has been paid to the temporal aspect of IAQ measurements. Identification and resolution of IAQ problems has been hindered because investigations only document "snapshots" of building conditions. Thus, the time and duration of measurements are an integral aspect of IAQ investigations. For example, complaint frequency can vary by season and even day of the week (27). And it has been reported that complaints occur at higher frequency in the summer and winter months. Concerning the day of the week, Monday can be a factor. One investigator reports Monday to have the highest rate of occurrence (i.e., "Monday sickness") (28). Thus, the investigation may not provide representative results due to changes in building function, occupant density, season, and ventilation system operation.

Questionnaires, Interviews, and Diaries

The purpose of questionnaires, as well as the use of occupant interviews and personal diaries, is to characterize the building population, to identify patterns of health and comfort complaints, and to determine the nature of symptoms and complaints being reported (11,20). Questionnaires are used in all of the published IAQ protocols, but the way in which they are used varies. The use of occupant interviews also is common, and used in nine of the 13 protocols (5,6,14-20). Diaries are much less frequently used. All eight of the solution-oriented protocols use both questionnaires and interviews, and two of the eight use diaries as well (5,14).

Some sources regard questionnaires as indispensable, while others put little emphasis on them. Others believe that questionnaires cause more problems than they solve (i.e., result in more complaints from occupants). NIOSH has found that the questionnaire is beneficial when administered early in the investigation, but warns that it must be carefully designed and executed by professionals in environmental health with an understanding of representative sampling (15). Light and Presant state that unless the questionnaire is administered in a representative fashion with a high rate of return, the results will tend to favor complainants (5). Furthermore, questionnaires that compare carefully selected areas and achieve a relatively high rate of return provide the best data for IAQ surveys (5). On the other hand, Lane, formerly of Honeywell Indoor Air Quality Diagnostics points out that [TABULAR DATA FOR TABLE 6 OMITTED] while questionnaires may be valuable tools for epidemiologists, they are easily misapplied in individual situations (15). Lund and Rice, based on a study using NIOSH's standard questionnaire, found the questionnaire to be useful in cataloging environmental conditions and symptoms when used as the initial survey instrument for assessing the number and distribution of reported symptoms (29). They concluded that with the use of a questionnaire, it is possible to conduct a more efficient building characterization and walk-through without general and more costly testing and air monitoring of the ventilation system (29).

To date, it is widely understood that for the questionnaire to be of value in an IAQ investigation it must be administered, analyzed, and interpreted by those skilled in their use. Furthermore, the questionnaire should be random, administered in both complaint and non-complaint areas, short, confidential, pretested, and carefully structured.

Another discrepancy involves the point during an investigation at which the questionnaire is administered. Questionnaires are usually administered in the early stages of the investigation, usually during the initial site visit, which helps to develop more effective strategies in dealing with the problem (15). However, several other protocols use a questionnaire later in the investigation (10-12,16,20). Woods gives the explanation for the delayed use of questionnaires that questionnaire responses should be obtained at the same time objective measurements are made, so as to elicit any real-time relationships indicative of environmental factors affecting occupant comfort (12).

Woods and Lane use a questionnaire based on the four major attributes of the indoor environment: acoustics, air quality, lighting, and temperature (10,12). These attributes are rated in terms of acceptability over a range from one to six with six being "very acceptable." Acceptability is chosen as the value of five, based on the emphasis ASHRAE places on ventilation and comfort standards. Each occupant is then asked to rate the acceptability of the indoor environment. Thus, after administering the questionnaire, if 80% or more of the occupants rate the overall indoor environment as a five or better, the indoor environment is considered acceptable (12).

The use of occupant interviews is an alternative to the use of questionnaires and is often recommended in place of questionnaires (5,6,14,15,17,18-20). As with questionnaires, basic information solicited includes symptom patterns, problem awareness, prior health conditions, and timing patterns (14). It is best to conduct the interview in private and include information regarding management relations and job satisfaction (6,18). It is also important to interview both management and employees (15). Advantages of the occupant interview include the opportunity to ask follow-up questions and request corroborating information. A disadvantage is that only a limited number of occupants can be interviewed due to time constraints, and responses may be biased (5).

Another option used for documenting complaint patterns involves having each occupant [TABULAR DATA FOR TABLE 7 OMITTED] maintain a personal diary (5,14). Occupants are asked to record date, time, observations about duration of symptoms, weather conditions, maintenance, etc. The personal diary can also be used to record daily observations of symptoms and building conditions. An advantage of using a personal diary is the reduction of memory bias of interviews and questionnaires. However, keeping a diary can be time-consuming and may delay resolution of the problem.

Medical Evaluations

Another contrasting point involves the use of medical evaluations. Several protocols do not mention the use of medical evaluations at all (16,20) and Hansen states that medical confirmation "supplied a couple months later may be interesting, but hardly vital to the building manager who has the problem" (15). Medical evaluations are an important component of most other protocols because it is vital to determine whether the symptoms are building-related and disappear when the person leaves the work environment (5,6,10,12,13,18). The medical evaluation is usually performed at an early stage of the investigation. However, two protocols use medical evaluation later in the investigation (6,12). The role of medical evaluations in IAQ investigations is virtually the same as that found with traditional occupational and environmental exposures.

Protocol Verification

Protocol verification is lacking with most approaches, and in those approaches using it, verification is often vague in terms of identifying both the problems and the successes with the recommendations. Quinlan et al., discuss verification procedures that include a surveillance program and follow-up medical and environmental evaluations (6). The purpose of the surveillance program is to follow the incidence of the problem, to detect cases early, and to provide ongoing referral and access to appropriate treatment. Follow-up medical exams and environmental evaluation via questionnaires or monitoring can be valuable in assessing whether the problem is getting worse or whether the implemented controls are effective. Light et al., also recommend continual tracking of complaints over time (5), and Woods et al., and Lane et al., use Quantitative Diagnostics to validate hypotheses and verify the effectiveness of recommendations (12,10).

Conclusion

The current IAQ investigation protocols are very similar in approach. The protocols begin with general observations, proceed to collect more specific data as indicated, and end with conclusions and recommendations. The ventilation system receives particular attention in nearly all of the protocols. A major problem affecting all of the current protocols is the lack of IAQ standards. Several inconsistencies were found among the protocols. The use of questionnaires, occupant interviews, personal diaries, and the use of medical evaluations (along with the point during the investigation at which they are administered) were found to vary considerably. Another inconsistency involves the use of verification procedures. None of the current protocols have been evaluated in regard to their effectiveness in identifying and subsequently solving IAQ problems.

There is much work needed in the area of IAQ investigation protocols. More research regarding multiple exposure to low-level contaminants and the development of IAQ standards is necessary. Finally, a proactive protocol that could identify problems prior to the manifestation of occupant complaints would be a tremendous benefit to solving IAQ problems.

Editor's note: An appendix of abbreviations used in this paper appears on page 35.

Acknowledgements

This research was supported by the Georgia Power Company and the University of Georgia's Agricultural Experiment Station. The authors would also like to thank Max Keifer of NIOSH Region IV in Atlanta, Georgia for assistance in collecting information.

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Indoor Air Quality

Abbreviations

ACGIH: American Conference of Governmental Industrial Hygienists 

AIHA: American Industrial Hygiene Association 

ANSI: American National Standards Institute

ASHRAE: American Society of Heating Refrigerating and Air-conditioning Engineers

CFUs: Colony Forming Units

DBRI: Danish Building Research Institute

EH&E: Environmental Health and Engineering

EPA: Environmental Protection Agency 

HVAC: Heating, Ventilating and Air-conditioning

IAQ: Indoor Air Quality

MOL: Ministry of Labor

NAAQS: National Ambient Air Quality Standards

NIOSH: National Institute for Occupational Safety and Health 

OSHA: Occupational Safety and Health Administration

PWC: Public Works Canada

Corresponding Author: Dr. Phillip L. Williams, Associate Professor, Environmental Health Science Program, College of Agricultural and Environmental Sciences, University of Georgia, Athens, GA 30602.