An Introduction to Indoor Air Quality (IAQ)
Nitrogen Dioxide (NO2)
Basic Information on Pollutants and Sources of Indoor Air Pollution
- Biological Pollutants
- Carbon Monoxide (CO)
- Formaldehyde/Pressed Wood Products
- Lead (Pb)
- Nitrogen Dioxide (NO2)
- Radon (Rn)
- Respirable Particles
- Secondhand Smoke/ Environmental Tobacco Smoke
- Stoves, Heaters, Fireplaces, and Chimneys
- Volatile Organic Compounds (VOCs)
The two most prevalent oxides of nitrogen are nitrogen dioxide (NO2) and nitric oxide (NO). Both are toxic gases with NO2 being a highly reactive oxidant and corrosive. The primary sources indoors are combustion processes, such as unvented combustion appliances, e.g. gas stoves, vented appliances with defective installations, welding, and tobacco smoke.
- Sources of Nitrogen Dioxide
- Health Effects Associated with Nitrogen Dioxide
- Levels in Homes
- Steps to Reduce Exposure
- Standards or Guidelines
- Additional Resources
Sources of Nitrogen Dioxide
Kerosene heaters, un-vented gas stoves and heaters. Environmental tobacco smoke.
Health Effects Associated with Nitrogen Dioxide
Eye, nose, and throat irritation. May cause impaired lung function and increased respiratory infections in young children. EPA's Integrated Risk Information System profile for Nitrogen Dioxide - epa.gov/iris/subst/0080.htm.
NO2 acts mainly as an irritant affecting the mucosa of the eyes, nose, throat, and respiratory tract. Extremely high-dose exposure (as in a building fire) to NO2 may result in pulmonary edema and diffuse lung injury. Continued exposure to high NO2 levels can contribute to the development of acute or chronic bronchitis. Low level NO2 exposure may cause increased bronchial reactivity in some asthmatics, decreased lung function in patients with chronic obstructive pulmonary disease and increased risk of respiratory infections, especially in young children.
Levels in Homes
Average level in homes without combustion appliances is about half that of outdoors. In homes with gas stoves, kerosene heaters, or un-vented gas space heaters, indoor levels often exceed outdoor levels.
Steps to Reduce Exposure
Venting the NO2 sources to the outdoors, and assuring that combustion appliances are correctly installed, used, and maintained are the most effective measures to reduce exposures.
(These are the same steps as those used to reduce exposure to carbon monoxide).
- Keep gas appliances properly adjusted.
- Consider purchasing a vented space heater when replacing an un-vented one.
- Use proper fuel in kerosene space heaters.
- Install and use an exhaust fan vented to outdoors over gas stoves.
- Open flues when fireplaces are in use.
- Choose properly sized wood stoves that are certified to meet EPA emission standards. Make certain that doors on all wood stoves fit tightly.
- Have a trained professional inspect, clean, and tune-up central heating system (furnaces, flues, and chimneys) annually. Repair any leaks promptly.
- Do not idle the car inside garage.
Standards or Guidelines
No standards have been agreed upon for nitrogen oxides in indoor air. ASHRAE and the US. EPA National Ambient Air Quality Standards list 0.053 ppm as the average 24-hour limit for NO2 in outdoor air.
Office of Air and Radiation page Nitrogen Dioxide "Six Common Pollutants"
Indoor Air Pollution: An Introduction for Health Professionals
Assists health professionals (especially the primary care physician) in diagnosis of patient symptoms that could be related to an indoor air pollution problem. Addresses the health problems that may be caused by contaminants encountered daily in the home and office. Organized according to pollutant or pollutant groups such as environmental tobacco smoke, VOCs, biological pollutants, and sick building syndrome, this booklet lists key signs and symptoms from exposure to these pollutants, provides a diagnostic checklist and quick reference summary, and includes suggestions for remedial action. Also includes references for information contained in each section. This booklet was coauthored with the American Lung Association, the American Medical Association, and the U.S. Consumer Product Safety Commission.