Nitrogen Dioxide and IAQ

The two most prevalent oxides of nitrogen are nitrogen dioxide (NO2) and nitric oxide (NO) according to the U.S. Environmental Protection Agency (EPA). Both are toxic gases with nitrogen dioxide being a highly reactive oxidant and corrosive.
Nitrogen dioxide primarily gets in the air from the burning of fuel. It forms from emissions from cars, trucks and buses, power plants, and off-road equipment. Indoors, the primary sources listed by EPA also come from combustion processes, from:
• Unvented combustion appliances, such as gas stoves
• Vented appliances with defective installations
• Welding
• Tobacco smoke
• Kerosene heaters
EPA goes on to share that the average level of nitrogen dioxide in homes without combustion appliances is about half that of outdoors. In homes with gas stoves, kerosene heaters or unvented gas space heaters, indoor levels often exceed outdoor levels.
The agency warns that health effects associated with exposure to nitrogen dioxide may include the following:
• 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:
o increased bronchial reactivity in some asthmatics
o decreased lung function in patients with chronic obstructive pulmonary disease (COPD)
o increased risk of respiratory infections, especially in young children
Fortunately, there are a number of steps people can take to reduce their exposure indoors. There are also professionals that can test for nitrogen dioxide and provide resources to mitigate exposure risks. They include 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
These are just a few of the many things to know about nitrogen dioxide as an indoor air quality exposure concern. To learn more about this or other air quality, industrial hygiene, environmental, health or safety issues, please visit the websites shown below.
Clark Seif Clark www.csceng.com
EMSL Analytical, Inc. www.emsl.com
LA Testing www.latesting.com
Zimmetry Environmental www.zimmetry.com
CTSI www.ctsiweb.com
Healthy Indoors Magazine www.healthyindoors.com