IDPH Guidelines for Indoor Air Quality

The Illinois Department of Public Health (IDPH) has developed voluntary guidelines for acceptable indoor air quality, recommendations for achieving acceptable indoor air quality, and a basic approach for indoor air quality investigations. Acceptable indoor air quality means that the air is free of excessive levels of chemical and physical contaminants and microbiological hazards (410 Illinois Compiled Statutes 87/10). These guidelines are not enforceable by law but are designed to help individuals or groups improve indoor air quality in their homes, schools, and workplaces.

The voluntary guidelines are intended to protect the general population, but may NOT be appropriate for sensitive individuals. Additionally, IDPH knows that many contaminants may be responsible for indoor air quality problems. If you have concerns about a contaminant not listed in these guidelines, contact IDPH for assistance by calling 217-782-5830 or emailing DPH.Tox@illinois.gov.

IDPH has included occupational standards for the parameters discussed in this document. These occupational standards were developed for healthy working-age adult males and are based upon exposures of eight hours per day, five days per week. They are NOT appropriate for the home environment. People spend more time in their homes, and more susceptible persons, such as children and older people, may be present.

Carbon dioxide (CO₂) is a normal constituent of exhaled breath. It is commonly measured as a screening tool to evaluate whether adequate volumes of fresh outdoor air are being introduced to indoor spaces. The outdoor level of carbon dioxide is usually from 300 parts per million to 400 parts per million (ppm). The carbon dioxide level is usually greater inside a building than outside, even in buildings with few complaints about indoor air quality. If indoor carbon dioxide levels are 1,000 ppm or above, there is probably inadequate ventilation, and complaints such as headaches, fatigue, and eye and throat irritation may be prevalent.

Carbon dioxide itself may not be responsible for the complaints; however, a high level of carbon dioxide may indicate that other contaminants in the building may be present at elevated levels and could be responsible for occupant complaints.

Properly ventilated buildings should have carbon dioxide levels between 600 ppm and 1,000 ppm, with a floor or building average of 800 ppm or less. If average carbon dioxide levels within a building are maintained at less than 800 ppm, with appropriate temperature and humidity levels, complaints about indoor air quality should be minimized. If carbon dioxide levels are greater than 1,000 ppm, complaints may occur. Therefore, 1,000 ppm should be used as a guideline for improving ventilation. If a building exceeds this guideline, it should NOT be interpreted as a hazardous or life-threatening. An elevated carbon dioxide level only indicates an inadequate amount of outside air being brought into a building.

Carbon monoxide (CO) is colorless, odorless, and a normal constituent of exhaust gases from incomplete combustion. Potential sources inside a building that may generate carbon monoxide include gas heating systems, gas stoves, gas water heaters, cigarette smoke, and portable kerosene heaters. For office areas, levels of CO are normally between 0 ppm and 5 ppm. Levels greater than 5 ppm may indicate the presence of exhaust gases in the indoor environment and should be investigated. Levels of carbon monoxide inside buildings should not exceed 9 ppm. Exposure to carbon monoxide at levels as low as 35 ppm may cause mild fatigue.

IDPH recommends that all buildings with indoor combustion sources install CO detectors approved by Underwriters Laboratories (UL) to continuously monitor for this gas. Every Illinois home is required to have at least one CO alarm in an operating condition within 15 feet of every room used for sleeping purposes. Schools are also required to be equipped with alarms or detectors. If an alarm activates, immediately evacuate your home or building and call 911. For more information, visit our carbon monoxide fact sheet or the Office of the Illinois State Fire Marshal.

Formaldehyde (HCHO) is a common constituent of adhesives used in particle board, carpeting, and furniture. The use of formaldehyde has been modified in recent years to reduce its release from these products. Increased ventilation during and following renovation or new construction should reduce the level of formaldehyde. IDPH recommends that the level of formaldehyde not exceed 0.03 ppm.

Hydrogen sulfide (H₂S) is a normal constituent of sewer gas. It is colorless and has an odor like rotten eggs. Sources of hydrogen sulfide in buildings usually arise from dry plumbing drains or broken sewer lines. The level at which people can begin to smell the gas is about 0.01 ppm. IDPH recommends that hydrogen sulfide levels be kept at less than 0.01 ppm, since an odor indicates the presence of sewer gas inside a building. An investigation should be conducted immediately after noticing a hydrogen sulfide odor to identify and correct the source. An Illinois-licensed plumber may be able to help determine the source and correct problems if flushing dry plumbing drains doesn’t work.

Nitrogen dioxide (NO₂) is a respiratory irritant produced during the incomplete combustion of natural gas or other fuels. IDPH recommends that the level of nitrogen dioxide not exceed the U.S. Environmental Protection Agency’s (USEPA) National Ambient Air Quality Standard (NAAQS) of 0.05 ppm over a 24-hour period. Ensuring that gas stoves, furnaces, water heaters, wood stoves, and other combustion appliances are properly installed and maintained will reduce exposure to NO2. Use a higher fan setting when cooking on a gas stove, and use the back burners for greater efficiency. When replacing a gas stove, consider choosing an electric or induction stove.

Ozone (O₃) is a respiratory irritant produced by equipment that uses high-voltage electricity. Photocopiers and ozone-generating air cleaners can release ozone into the indoor environment. IDPH recommends that ozone levels not exceed 0.07 ppm. You can limit your exposure indoors by avoiding portable air cleaners that generate ozone. The California Air Resources Board has a list of air cleaning devices that have been certified for low ozone emissions.

Particulate matter contains solid or liquid droplets that are so small that they can be inhaled and cause serious health problems. Some particles less than 10 micrometers in diameter (PM₁₀) can get deep into your lungs, and some may even get into your bloodstream. Of these, particles less than 2.5 micrometers in diameter, also known as fine particles or PM_2.5, pose the greatest health risk.

IDPH recommends that PM₁₀ be maintained at less than the USEPA NAAQS of 150 micrograms of particulates per cubic meter of air (µg/m³) and particulates 2.5 micrometers in diameter or less (PM_2.5) be maintained at less than the NAAQS of 35 µg/m³ during a 24-hour period. On days when the Air Quality Index is unhealthy, close your windows and doors and use a portable air cleaner with HEPA filters. Avoid smoking, frying food, and burning candles or incense.

Radon (Rn) is a colorless, odorless, radioactive gas naturally produced when uranium decays in the soil. Uranium and its decay products are commonly found in soil and rock in Illinois. Radon gas enters buildings through cracks, crawlspaces, basement drains, and other foundation or concrete slab openings. The gas decays into radioactive particles that, when inhaled, cause cell damage and potentially lung cancer. Radon gas is the second leading cause of lung cancer in the United States, and the leading cause of lung cancer among non-smokers.

IDPH recommends that levels in homes be less than 4.0 picocuries per liter (pCi/L). If levels exceed 4.0 pCi/L, radon mitigation should be considered to reduce the risk of adverse health effects. The only way to determine the radon level in your home is to have the air tested. The Illinois Emergency Management Agency can provide a list of businesses and laboratories that conduct radon testing or that have test kits for sale. Visit www.radon.illinois.gov or call 800-325-1245 for additional information.

There is no “ideal” humidity level and temperature suitable for all building occupants. Many factors, such as personal activity and clothing, may affect personal comfort. Acceptable relative humidity levels should range from 30% to 60%year-round. Levels less than 30% in the winter and greater than 60% in the summer should be considered unacceptable. Elevated relative humidity can promote the growth of mold, bacteria, and dust mites, which can aggravate allergies and asthma. Use dehumidifiers to control humidity and reduce dampness.

IDPH recommends that indoor temperatures in the winter be maintained between 68°F and 75°F. Temperatures in the summer should be maintained between 73°F and 79°F. These ranges should be acceptable for sedentary or slightly active persons.

ASHRAE Standard 62.1 specifies minimum ventilation rates and other measures intended to provide acceptable indoor air quality and minimize adverse health effects. Proper thermostat location and a well-maintained heating, ventilation, and air conditioning (HVAC) system should allow temperatures to be maintained within the thermal comfort range. Operating a building under positive pressure will reduce the infiltration of outside contaminants into a building. Using local exhaust in areas such as copy rooms, chemical storage areas, and print shops can reduce other sources of indoor air contaminants.

Building owners should also consider source control since it can have a major impact on indoor air quality. Construction, painting, and roofing should be performed while areas are unoccupied. During renovation activities, ventilation systems should be operated 24 hours a day. Increased ventilation during and after these activities will reduce the impact on indoor air. “Dry” furnishings and materials, such as carpeting, tile, textiles, and wood products, when appropriate, should be allowed to “air out” for a minimum of three days before installation, or until there is no noticeable odor or irritation. “Wet” materials, such as adhesives, glazes, caulks, and paints, should be used sparingly. “Dry” furnishing materials should not be installed until “wet” materials have been allowed to dry.

Concerning filtration and air cleaning, IDPH recommends installing the highest efficiency filters your residential furnace or HVAC system can handle. Further, using portable air cleaners with HEPA filters, especially in higher-risk areas or locations where ventilation is poor, can help reduce exposure to particulate matter and infectious aerosols.

Investigation of indoor air quality problems is not an easy task. The IDPH approach to indoor air quality investigations follows the methods developed by the National Institute for Occupational Safety and Health (NIOSH) in their publication, Guidance for Indoor Air Quality Investigations. This NIOSH technique is best described as one of exclusion. The investigation tries to narrow the range of possible problem causes. IDPH has found six primary sources of indoor air quality problems:

1. Inadequate Ventilation: These problems involve a lack of adequate fresh air and uneven distribution of fresh air within a building.
2. Humidity and Temperature: These problems involve parameters outside the normal comfort range.
3. Inside Contamination: Some investigations identified copy machines, office products, and chemicals used or stored indoors as significant sources of indoor air problems.
4. Outside Contamination: This is caused when previously exhausted contaminants or odors are drawn back into a building, generally caused by improper air intake placement or periodic changes in the wind conditions. A common problem is vehicle exhaust fumes from parking garages or loading docks drawn into a building's ventilation system.
5. Microbial Contamination: This problem is usually associated with water leaks, water infiltration, elevated indoor humidity or dampness, humidifiers, and contaminated ventilation ductwork.
6. New Building Materials: This results from building materials (including carpeting) releasing gases into the air during and shortly after the materials are first installed. Increased ventilation after installation will enhance the dissipation of these chemicals. These problems usually resolve with time.

Typical indoor air investigations will include a review of several items:

• visual inspection and plan review of the HVAC system
• observation of conditions in the area of concern
• interviews with individuals experiencing problems
• measurement of ventilation and comfort parameters (carbon dioxide, humidity, temperature, and carbon monoxide)

A general walk-through evaluation of the building should be performed, noting specifically:

• water-damaged ceiling, wall, and floor finishes
• dust streaking near air vents and diffusers
• mold growth on building components
• apparent building use changes
• the presence of odors
• condition and utility of outside air dampers
• condition of the air filtration system

Illinois Department of Public Health
Environmental Toxicology Program
525 W. Jefferson St.
Springfield, IL 62761

217-782-5830
TTY (hearing impaired use only) 800-547-0466
DPH.Tox@illinois.gov

American Industrial Hygiene Association

U.S. Environmental Protection Agency