Subject : IAQ FAQ part 3


10.1 How do ventilation systems affect IAQ?

Ventilation systems can bring in pollutants from outside; they can be the source of pollutants; they can cause pollutants to flow from one location in a building to another; or they can fail to dilute or remove pollutants from a building or a portion of it. When you add these factors up, you have the single biggest cause of IAQ problems: improperly designed, installed, operated, or maintained ventilation systems.

Some of the most commonly brought-in outside air pollutants are smog; elevated mold spore or pollen levels, due to seasonal growth; vehicle exhaust from nearby loading docks; Legionella, other bacteria, or biocides from adjacent cooling towers; mold spores, bacteria, yeasts or algae from standing water or decaying vegetation near outside air intakes; or fumes from exhausts improperly located so they are brought right back in to the building.

The most common pollutants generated within a ventilation system are mold spores and bacteria, from water problems, especially standing water in condensate pans and rain leaks; fiberglass from deteriorating insulation; and general dirt and debris from a system that's gone too long without cleaning or has been improperly filtered.

Improper pressure relationships can direct pollutants where they don't belong. For example, bathrooms have exhaust fans to remove odors, bacteria, etc. If there is a supply vent in the bathroom that's more powerful than the exhaust (perhaps because the exhaust has gotten dirty) then air will flow from the bathroom to adjacent areas. Leaking ducts in an attic can direct air from the attic into occupied spaces.

Tightly constructed buildings, as are most modern commercial buildings, depend on fresh air supplied by the ventilation system to dilute contaminants normally generated and present within a building. There are always some; when fresh air supplied is insufficient, they can build up to a point where they become a problem for people.

The most common causes of insufficient fresh air supply are, in order of frequency, 1) thermostat fans settings of "auto" causing fans to run only when heating or cooling is called for, 2) units turned off or incorrectly set timers causing systems to not run during hours of occupancy, 3) no outside air intakes at all or outside air intakes completely shut, 4) building constructed under earlier building codes allowing inadequate fresh air supply, 5) usage changes rendering the amount of outside air supplied no longer adequate, 6) improper modulation of outside air volume ("economisers" that shut outside air off completely, and "VAV" systems with heat load changed or improperly calculated).

On 4) above, it should known that until recently, code requirements for amounts of outside air required reflected reduced levels considered acceptable for energy saving purposes, dating to the 1970's. In some areas this is still the case, with code requirements not having caught up with currently accepted standards. In addition, any building constructed under earlier code requirements would be legal with fresh air supply amounts which are too small per current standards.

10.2 How to tell if there is a problem.

Any of the following indicates a problem with the ventilation system and IAQ: There is an odor issuing from the vents. You see pieces of fiberglass caught in grilles, or find debris on desks in the morning below vents. You can smell odors when you first walk in such as people's perfume, cooking odors, bathroom odors, solvents. People start sneezing or their noses run when the A/C fan comes on. The systems are more than 10 years old and have never been cleaned (unless the filtration is unusually good). Thermostats are under the control of occupants who can turn them on or off at will, adjust temperature to anything they like. The air is stale, stuffy, or dead.

10.3 Preventing ventilation IAQ problems.

Run fans continuously from prior to occupancy through all hours of occupancy. Ensure that there are open outside air intakes and no obvious source of pollutants in front of them. Put thermostats under lock and key or better, use programmable thermostats that allow occupants to adjust the temperature up or down a few degrees for comfort, but no other changes. Inspect the interior of systems frequently; every three months for condensate pans. Allow no standing water or water incursion into ventilation systems and clean it up promptly when it occurs.

If possible, remove all fiberglass exposed to air streams or replace it with non-fiberglass insulation. At the least, coat it with a hard-surfaced anti-microbial registered for this purpose. Replace any fiberglass that has gotten wet. Eliminate any microbial contamination as fast as it starts.

Clean air handlers yearly and ducts every 5 to 10 years or as needed. Use the best possible filtration that your system can handle. Have ventilation systems isolated from areas under remodel. Supply maximum possible (preferably 100%) outside air following construction or major remodels. Have new buildings commissioned to ensure ventilation systems are working as designed. Have ventilation systems re-assessed in the course of any significant usage change. Have your ventilation system upgraded to comply with current standards (ASHRAE standard 62-1989, see section 11.6) and building codes.

10.4 Solving ventilation IAQ problems.

Go through the points covered in 10.3 and correct anything found.

10.5 Duct cleaning.

Ventilation systems get dirty and cleaning them periodically is necessary for the efficiency and longevity of the system. It also impacts IAQ, though this is somewhat controversial, since the studies haven't been done to prove it.

There are six methods of duct cleaning. Four of them don't work; only one is really effective.

a. Shop vacuum hooked up to the end of a duct or waved around inside. Doesn't work.

b. Spray some kind of sealant (glue) inside the duct to cover up and (theoretically) seal the dirt in. Doesn't work, as coverage of the interior of the duct is spotty and tends to create new problems such as affecting fire rating. If the coating contains an anti-microbial, the occupants are now exposed to biocides. The sealant can dry up and blow out. Not recommended by the U.S. EPA.

c. Truck mounted vacuum or portable high power vacuum. Doesn't work. Air flow at the edge of the duct is minimal no matter how powerful the vacuum and if too powerful it can collapse the duct or cause it to leak thereafter.

d. Truck vacuum or portable high powered vacuum with addition of an "air whip" - compressed air to (supposedly) loosen the dirt from the walls of the duct. Works poorly as doesn't remove caked-on dirt.

e. Truck vacuum or portable high powered vacuum with addition of some sort of compressed air and brush system. Works fairly well if done very conscientiously in relatively small diameter metal duct. Sometimes the only system that can be used in inaccessible ducts.

f. Brush and vacuum using HEPA filtered portable vacuum cleaners. Done by opening up enough access points into the ducts to allow direct inspection and cleaning with HEPA filtered brush and vacuuming systems. This allows a verified thorough cleaning of the interior and of internal components such as turning vanes, dampers, seams, etc. Can't be used on inaccessible duct.

Having duct cleaning done by any methods other than (e) and (f) is likely to lead to regrets and will certainly lead to the job needing to be re-done sooner than it should be. A properly done duct cleaning job doesn't need to be done again for another 5 to 15 years (in nearly all cases), depending on factors such as dirtiness of the environment and quality of filtration.


11.1 What licensing requirements are there for IAQ practitioners?

There are none.

11.2. So how do I choose someone?

Hiring a professional to assist in evaluating an indoor air quality problem is adventurous. There are no licenses, degrees, certifications, etc. which mean much in this field.

There are however some pieces of advice I can give.

Only hire someone who specializes in IAQ investigations. Not someone who also cleans ceiling tiles, does general industrial hygiene work, or groundwater remediation.

There are few competent practitioners; perhaps only a few dozen in the entire U.S. You may be able to get names from agencies such as your state occupational safety and health administration, or the American Lung Association.

Anyone claiming to be a professional should be able to provide references of successful similar projects. They must be able to competently evaluate an HVAC system in regards to IAQ, since most IAQ problems involve the HVAC systems. Make sure that the person actually looks inside ventilation systems.

They must be pretty competent in environmental microbiology, since many IAQ problems involve microbial contamination. Few people know how to competently evaluate such.

They should put more emphasis on their inspections than on their tests. Someone who is going to crawl inside your air handlers or under your house and look is going to be more valuable than someone who walks in, plunks down some fancy equipment, and take a bunch of measurements without ever looking around.

The most important tools in an IAQ investigation are the eyes and nose of the investigator. Therefore beware of anyone who proposes only to come in and do a bunch of tests, and who does not emphasize inspection as the most important part of the work.

If I had to choose between two practitioners, without having the luxury of knowing anything else about them, and one was a P.E. (licensed professional engineer), I would choose the P.E. In my experience, a majority of competent IAQ practitioners are P.E.'s (though there are incompetent P.E.'s, too, and competent IAQ practitioners who aren't P.E.'s - me for example).


12.1 Overview.

IAQ is in general hardly regulated at all. There are some codes, statutes, and regulations which cover some points. The only specific codes are likely to be building codes applicable at the time the building was permitted. Some very general statutes can (and often are) applied to IAQ situations. There are some specific standards and guidelines.

12.2 U.S. OSHA "General Duty" clause.

The so-called "general duty" clause in OSHA (Occupational Safety and Health Administration) regulations, requires employers to provide a safe and healthful work environment for employers. If OSHA (or your state version of it) does get involved in an IAQ situation, chances are this will be the basis.

12.3 U.S. OSHA "Hazard Communication Standard"

The Hazard Communication Standard requires employers to formally notify employees of exposure to chemicals which may be hazardous to their health. In rare cases this will apply to IAQ problems. An example would be if the inside of a building is massively contaminated with a toxigenic mold.

12.4 Proposed U.S. OSHA standards.

In April of 1994, OSHA proposed for the first time, indoor air quality rules which would apply to every commercial facility in the U.S., including offices, government buildings, medical facilities, schools, retail stores, even break rooms in industrial plants.

There were two major portions to this proposed rule-making. One part dealt with tobacco smoking, basically barring smoking in any area of a commercial facility except for dedicated smoking lounges. This has been fought tooth-and-nail by the tobacco industry.

The other part of the rules deals with general indoor air quality issues. It requires actions such as periodic inspections, record keeping, ensuring that ventilation systems are operating as designed, and response to IAQ complaint situations.

A final rule issuance is planned for later this year (1995) though there is some doubt if this will actually occur.

12.5 Public health.

In some cases, indoor air quality issues can become a public health issue, with County Health Departments involved, and possible building closure. Outbreaks of Legionnaire's disease are one possible scenario. Others are possible. However, Health Departments rarely get involved in IAQ situations unless very serious. Fire department hazardous material teams will often respond to serious acute incidents, e.g., carbon monoxide poisonings, waves of nausea or fainting resulting in a building evacuation, etc. Neither type of agency is normally equipped or inclined to deal with routine IAQ situations, e.g., sick building syndrome cases.

12.6 ASHRAE standard 62-1989

ASHRAE (American Society of Heating Refrigeration and Air- Conditioning Engineers) has promulgated a national consensus standard, 62-1989, "Ventilation for Acceptable Indoor Air Quality". This document specifies the amount of outside air to be supplied to different types of facilities; it specifies some things in regards to design and operation of ventilation systems; and it specifies some things in regards to contaminants in the air.

It is the single most referred to document in regards to indoor air quality issues.

It is also currently under revision, however, the committee involved in this is having a great deal of difficulty coming to agreement on it, even before it goes out for public comment. Committee members include IAQ experts as well as representatives of the tobacco industry, commercial building owners, union representatives, and others. Stay tuned on this one.

12.7 ARI guidelines

The Air-Conditioning and Refrigeration Institute, the industry trade group for air-conditioning system manufacturers, has published a booklet of guidelines for design, installation, and maintenance of A/C systems for good air quality. This booklet provides most of the basic information one should know on these issues.

12.8 ACGIH guidelines

The ACGIH (American Conference of Governmental Industrial Hygienists) has published a manual called "Guidelines for the Assessment of Bioaerosols in the Indoor Environment". While it doesn't go into great detail, it provides all the most important basic data on this subject.

ACGIH also issues exposure limits for chemicals in the workplace, called "Threshold Limit Values", which are widely used in assessing whether excessive chemical exposure has occurred.

12.9 Legal precedents.

I am not a lawyer, and the following is a lay person's summary of what I know about the subject. See an attorney if you are serious about pursuing legal recourse (or if you are being sued). There have been many lawsuits filed on IAQ; nearly all have been settled out of court, some for substantial amounts of money.

Only one lawsuit in the U.S. has to date gone all the way through the court system, resulted in a jury decision, and award for the plaintiffs. This was a suit of some EPA employees against the owners and managers of the EPA headquarters building in Washington D.C. Five employees were awarded a total of $950,000, an amount which probably didn't cover the legal fees involved. The case is under appeal. If it stands up, it is important mainly because it establishes the owners and managers of a building as legally responsible for the indoor air quality affecting the health of occupants.

12.10 Building codes

Building codes vary from place to place. There are several points on which they specify things of importance to indoor air quality. They normally specify for commercial structures the amount of outside air that is to be supplied by the ventilation system. In addition, they are often very specific on points of construction which may affect such things as carbon monoxide problems, moisture entry into the building, and re-entry of exhaust fumes.

The codes that apply to a building are those that were in force at the date the building was permitted, following construction or remodel. Codes change slowly, in response to changes in standards and scientific consensus. Therefore, even a new building may not be constructed in accordance with current scientific thought.

12.11 Individual state laws and regulations

This section is very much under construction, and information from others is very welcome.

Many states and municipalities have adopted regulations on tobacco smoking in the last year or two. More are coming into force as time goes on.

The State of Washington has adopted indoor air quality regulations. I do not have specifics on these.

The State of California has exactly one section in the code of regulations which applies to indoor air quality in commercial work places. Title 8, paragraph 5142 requires ventilation systems to be inspected yearly, and any faults to be promptly corrected. It also requires that ventilation systems operate as intended in terms of fresh air supply and that fans run continuously during hours of occupancy.

12.12 Non-U.S.

Sorry, I don't have any data on this. Your information is welcome!


There is no effort here to present anything like a complete bibliography of the subject. However, following are some of the best introductory texts on IAQ, with a line of description on each.

1. "Building Air Quality" (EPA and NIOSH, 1991). A pretty good general introduction to the subject.

2. "Guidelines for the Assessment of Bioaerosols in the Indoor Environment:" (ACGIH, 1989). The bible for assessing indoor microbial contamination problems.

3. "The Industrial Hygienist's Guide to Indoor Air Quality Investigations" (AIHA, 1993). This booklet provides a basic description of the protocols for performing indoor air quality investigations followed, with some variations, by all reputable investigators.

4. "Indoor Air Pollution Control", by Thad Godish (Lewis Publishers, 1989). Loaded with tons of specific data on indoor air quality problems and solutions.

5. "Biological Contaminants in Indoor Environments" (ASTM, 1990). A series of articles on different biological pollutants. Lots of good information.

6. "Indoor Air Quality and HVAC Systems", by David W. Bearg (Lewis Publishers, 1993). Lots of data on ventilation systems design, operation, and maintenance in regards to IAQ.

7. "IAQ and HVAC Workbook", by D. Jeff Burton (IVE, Inc., 1993). A good, very simple introduction to the subject.

8. "NAFA Guide to Air Filtration" (NAFA, 1993). A very good manual on types of filters, applications, efficiency, etc.

9. "The Inside Story, A Guide to Indoor Air Quality" (EPA and CPSC, 1993). A booklet on residential indoor air quality.

10. "Understanding Indoor Air Quality", by Brooks and Davis (CRC Press, 1992). A good overview of the subject with lots of specific information.

11. "Guide for the Prevention of Microbial Growth in Ventilation Systems" (IRSST, 1994). An excellent, well-organized, and up- to-date manual.


There is no single organization which operates as, or is acknowledged as, the main player in the indoor air quality field. There are many organizations which have something to do with IAQ. Following are many ones I am aware of, what they have to do with it, and how to contact most of them. Most of them have publications catalogs. Some have toll-free hotline phone numbers.

AAFA (Asthma and Allergy Foundation of America). A consumer organization. Publishes books, including on ways to improve allergy and asthma conditions by improving the indoor air quality. 1125 15th St., NW, Suite 502, Washington, DC 20005. (202) 466-7643.

AEE (Association of Energy Engineers). The professional society of engineers in the fields of energy production and conservation. Certifies individuals as "Indoor Air Quality Professionals" through a qualification and test procedure. Sponsors seminars on indoor air quality. 4025 Pleasantdale Rd., Suite 420, Atlanta, GA 30340. (404) 447-5083.

AIHA (American Industrial Hygiene Association). The professional association of industrial hygienists. Publishes a research journal. Provides certification in the sub-specialty of "Indoor Environmental Quality" for Certified Industrial Hygienists. Publishes some IAQ related manuals and booklets. 2700 Prosperity Ave., Suite 250, Fairfax, VA 22031, (703) 849-8888.

ALA (American Lung Association). Publishes material, promotes research, sponsors conferences. 1740 Broadway, New York, NY 10019.

ARI (Air-Conditioning and Refrigeration Institute). Trade association of the A/C manufacturing industry, sets standards for equipment. 1501 Wilson Blvd., Suite 600, Arlington, VA 22209. (703) 524-8800.

ASHRAE (American Society of Heating, Refrigeration, and Air- Conditioning Engineers). The U.S. professional society of HVAC engineers. Publishes standards. Sponsors research. Publishes a research journal. Holds a yearly symposium on IAQ and publishes proceedings of it. 1791 Tullie Circle, N.E., Atlanta, GA 30329. (404) 636-8400.

ASTM (American Society for Testing and Materials). Standard setting organization. 1916 Race St., Philadelphia, PA 19103. (215) 299-5571.

AWMA (American Waste Management Association). A professional association in the fields of air pollution control, hazardous waste disposal, etc. Sponsors symposia on indoor air quality. P.O. Box 2861, Pittsburgh, PA 15230. (412) 232- 3444.

CDC (Centers for Disease Control). Actually a division of NIOSH, this is the U.S. government agency which gets involved in serious public health threats. They will get involved in, for example, serious Legionella outbreaks, or mysterious building indoor air quality situations with many people hospitalized, etc.

CPSC (Consumer Product Safety Commission). This is the U.S. government agency responsible for the safety of consumer products. As such they regulate such devices as humidifiers and room air cleaners. 11820 Coakley Circle, Rockville, MD 20852. Product Safety Hot-Line 1-800-638-CPSC.

EPA (Environmental Protection Agency). The U.S. government agency charged with protection of the environment, both indoor and outdoor. Has a small "Indoor Air and Radiation" division, which seeks to improve indoor air quality by publication of materials on the subject, and by persuading voluntary agreement to uphold improved standards. Has no enforcement authority in regards to indoor air quality. Sponsors research. Public Information Center (PM-211B), 401 M Street, S.W., Washington, D.C., 20460. (202) 382-2080. Has a hotline you can call with IAQ questions: 1-800-438-4318.

IRSST. The Quebec province version of OSHA. Publishes books and reports on indoor air quality, mostly in French, some in English, including a manual similar to the EPA's Building Air Quality, but better organized, and containing a lot of material the EPA manual lacks. Communication Division, 505, de Maisonneuve Blvd., West, Montreal (Quebec), Canada, H3A 3C2. (514) 288-1551.

ISIAQ (International Society of Indoor Air Quality and Climate). An international professional society of indoor air quality scientists. Publishes a quarterly research journal (the only one exclusively devoted to indoor air quality). Puts on a major international conference on indoor air quality every three years and publishes proceedings of it (next in Nagoya, Japan, 1996). P.O. Box 22028, Sub 32, Ottawa, Canada K1V 0W2. (613) 737- 2005.

NADCA (National Air Duct Cleaners Association). The professional association of ventilation system cleaning companies. Publishes standards on cleaning of ducts. Certifies duct cleaning companies (program just now beginning). 1518 K Street, NW, Suite 503, Washington, DC 20005. (202) 737- 2926.

NAFA (National Air Filtration Association). Association of air filter manufacturers. Publishes an introductory book on types of filters, their efficiency, applications, etc. 1518 K Street NW, Washington, DC 20005.

NCEHS (National Center for Environmental Health Strategies). A one-woman operation, one of the main forces in getting MCS taken seriously. 1100 Rural Ave., Voorhees, NJ, 08043. (609) 429-5358.

NCIAQ (National Coalition on Indoor Air Quality). A coalition of other organizations which have something to do with indoor air quality, including NADCA, NAFA, and others. Holds a yearly conference on indoor air quality.

NEHA (National Environmental Health Association). A private non-profit association, it is mainly involved in public health issues. They do publish a self-teaching guide and reference manual on indoor air quality. 720 S. Colorado Blvd., South Tower, Suite 970, Denver, CO 80222. (303) 756-9090.

NIOSH (National Institute of Occupational Safety and Health). The U.S. government research agency on the subject of occupational safety and health, including workplace indoor air quality. Performs and sponsors research. Publishes manuals. Has a publications department which provides many publications for free. NIOSH also has a hazard evaluation section which may send a team out to investigate your indoor air quality complaint situation, depending on the seriousness and uniqueness of the event. It may take some months for them to respond if they do take your case on, depending on backlogs. Requests for field evaluations: Hazard Evaluations and Technical Assistance Branch (R-9), 4676 Columbia Parkway, Cincinnati, OH 45226. (513) 841-4382. Information hotline: 1- 800-35NIOSH. Publications: (513) 533-8287.

NIST (National Institute of Standards and Technology). A U.S. government research agency which sets standards on methods of testing (formerly known as the National Bureau of Standards). Its Building And Fire Research Laboratory performs research on some aspects of indoor air quality, particularly measurement of ventilation efficiency, and makes results available in publications. Gaithersburg, MD 20899.

OSHA (Occupational Safety and Health Administration). The U.S. government agency responsible for workplace health and safety. They are primarily involved in industrial issues such as toxic chemical exposure, dangerous machinery, etc. However, as noted, they have now proposed indoor air quality rules for the commercial work place. Office of information: (202) 219-8151.

Most states have their own agencies which perform the functions within that state which are assigned to OSHA. Sometimes they have state regulations which are more stringent than federal regulations. How much they get involved in indoor air quality issues may vary; in California, they rarely get involved unless a relatively serious situation exists.

WHO (World Health Organization). International governmental organization which monitors and works to improve health conditions world-wide. Has a committee on indoor air quality which sponsors research, publishes findings, and issues guidelines in regards to indoor air quality.


15.1 This article is provided as is without any express or implied warranties. While every effort has been taken to ensure the accuracy of the information contained in this article, the author assumes no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. Users of this information are to understand that much of the contents of this FAQ consist of opinion and do not constitute accepted scientific theory, this being, after all, a field which is still young and under development. Therefore any actions by readers of this material are undertaken solely on their own responsibility.

15.3 My publication of this FAQ on the Internet does not grant anyone the right to re-publish or transmit it or any part of it in any form whatsoever nor through any medium, whether electronic, print, or otherwise, without express written permission from myself.

15.4 Much data has been taken from other sources, and I thank those who have contributed. The decision as to what to include and what not is mine, as is the decision as to what opinion to express where there is disagreement in the field. Any and all errors in this article are mine.

15.5 Copyright (C) 1995, Richard R. Byrd. All rights reserved.