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Indoor Air Quality

Background

Indoor Air Quality (IAQ) refers to the quality of air in non-industrial environments, such as offices. Since the energy crisis of the mid 1970s, IAQ has become an increasingly important issue for building owners, managers and occupants. The recent increase in IAQ complaints can be attributed to a decrease in building ventilation and a higher level of indoor-generated pollutants.

Poor building ventilation is a result of more energy-efficient construction and the use of mechanical ventilation instead of natural ventilation (windows). The indoor pollutant level has increased from the use of synthetics in building materials and office furniture, the use of chemical cleaning products and the increased use of office equipment—all of which contribute to chemical and particulate contamination of the indoor air.

Mechanical ventilation equipment can also contribute to indoor air contamination. In fact, it can be a source of dust, mold, bacteria and viruses. Improperly located air intake ducts will bring outside pollutants into the indoor environment.

Building occupants are yet another source of pollutants. Our metabolic processes are a source of many different volatile organic compounds—not to mention perfume, deodorant, hair spray and other grooming products that add contaminants to the indoor air.

Tobacco smoke is a very controversial contaminant. OSHA's proposed IAQ standard requires that a designated area with separate ventilation be provided in workplaces where smoking is allowed.

Results of Poor Indoor Air Quality

Two types of illness can result from contaminated indoor air. Sick Building Syndrome (SBS) is a physical reaction to multiple low-level contaminants. These contaminants could be chemical (formaldehyde), biological (mold) or physical (heat, humidity, lighting). Symptoms for SBS include headache, nausea, fatigue, eye irritation and respiratory irritation. These symptoms normally disappear when the afflicted individuals leave the building for a period of time—such as a weekend—but return when they reenter it.

Building Related Illness is the second health problem caused by contaminated indoor air. This differs from Sick Building Syndrome in that it is a physical reaction to a single identifiable contaminant found to be prevalent in the indoor environment. An example of Building Related Illness is Legionnaires Disease.

Building managers need to treat IAQ complaints seriously and deal with them promptly. These situations are often difficult to diagnose and solve. Quick action will help prevent other occupants throughout the building from thinking they might have SBS when they're really experiencing some other form of stress, such as being over-tired.

Mechanical Ventilation Systems

The purpose of mechanical ventilation systems is to bring in outside air and mix it with a percentage of return inside air, condition the air (heat, cool, humidify), and then distribute it to various areas of the building. The National Institute for Occupational Safety and Health (NIOSH) found that up to 52 percent of IAQ problems are a result of insufficient or ineffective ventilation.

Outside air is brought into buildings to dilute contaminants originating within the building. Insufficient outside air intake, either from improper system design or mechanical malfunction, can lead to contaminant buildup inside the space. Contaminated outside air brought into the building from poorly located intakes will also contribute to contaminant load in the building.

Very few problems would exist if only outside air was used to replenish exhaust air. The drawback to this solution is cost. Because of the expense, newer ventilation equipment is computer controlled to provide the most cost-effective mix of inside and outside air. Proper maintenance of mechanical ventilation equipment keeps the system cost-effective and functioning as designed. It also prevents the system from becoming a source of contaminants.

The American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) has specified limits on the amount of outside air that must be brought in and distributed to various parts of buildings. For example, office space requires 20 cubic feet of outside air per minute per occupant; a designated smoking area requires 60 cubic feet per minute per occupant.

Carbon dioxide, a gas which we all exhale, is a useful indicator of insufficient outside air intake and ventilation problems. OSHA's proposed IAQ standard requires that CO2 levels be maintained below 800 ppm and monitored on a quarterly basis. ASHRAE and NIOSH both specify 1000 ppm as an indicator of insufficient ventilation. The ambient outside CO2 concentration is approximately 300 ppm. Note: 800 ppm or 1000 ppm of carbon dioxide is NOT a hazardous concentration, but rather an indicator of potential ventilation problems. OSHA's permissible exposure limit for CO2 is 5000 ppm.

Air Monitoring

IAQ problems are difficult to diagnose and solve because of the large number and many types of contaminants or building stressors that can cause problems. The cumulative effect of many stressors (chemical, biological and physical) is often the most difficult to identify. An IAQ investigation begins with thorough research and investigation at the problem site to identify potential contaminants or stressors. No monitoring should be done until these items have been identified. The flowchart below shows just one possible approach to an IAQ investigation.

If air monitoring is necessary, comparative samples from non-problem areas of the building are a useful tool in determining what the possible contaminants are.

Following is a brief list of building stressors and contaminants and the type of equipment used to identify each one:

Note: This is not intended to be a complete list of contaminants. ASHRAE 62-1989 lists common contaminant levels for these and other specific chemicals.

Standards and Regulations

ASHRAE 62-1989—Ventilation for Acceptable Indoor Air Quality. Specifies minimum ventilation rates and indoor air quality needed to avoid adverse health effects to human occupants.

ASHRAE 55-1981—Thermal Environmental Conditions for Human Occupancy. Specifies minimal indoor thermal parameters (air temperature, humidity, movement) needed to avoid adverse health effects to human occupants.

Occupational Safety & Health Standards 1910.19—Special Provisions for Air Contaminants—Indoor Air Quality. (Proposed Rule)

Commonly Asked Questions

Sources for More Information

American Society of Heating, Refrigeration and Air Condition Engineers, Inc. (ASHRAE)
1791 Tullie Circle NE
Atlanta, GA 30329

EPA Indoor Air Quality Information Clearinghouse
P.O. Box 37133
Washington DC 20013-7113
Phone: 800-438-4318

NIOSH Guidance for Indoor Air Quality Investigations

National Institute for Occupational Safety & Health

Hazard Evaluation & Technical Assistance Branch
4676 Columbia Parkway, Cincinnati, OH 45226
Phone: 513-841-4374

NIOSH Information Line
Phone: 800-356-4674

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