For many people with healthy lungs they may never, or at least only rarely, think about what is in the air they breathe. When asked, people inevitably say oxygen makes up air, but this is only one component of what is in the air we all breathe.

So what is air made up of? The air around us is made up of a mixture of gases and particles that can vary by season, location, altitude and various weather and atmospheric conditions. However, the primary component of air is nitrogen at about 78%. Nitrogen is followed by oxygen at approximately 21% and argon at almost 1%.

Carbon dioxide, which many people recognize as a greenhouse gas, makes up only about 0.04%. There are also a number of other trace gases present in minute amounts that include neon, helium and methane to nitrous oxide, ozone and carbon monoxide to name a few.

Water vapor is also a component that can vary significantly from less than 1% up to 4% depending on location and conditions. Air also contains small particles that can be the result of both natural processes and manmade activities.

For people living in industrial areas or congested cities that are subject to high pollution levels, they can be exposed to a number of additional substances in the air. In the United States, the Clean Air Act requires the Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for six common air pollutants, also known as "criteria air pollutants". These include carbon monoxide (CO), lead (Pb), ground-level ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2) and particulate matter (PM).

Particulate matter is a mixture of microscopic solids and liquid droplets that may include everything from, but not limited to, smoke, ash and soot to dust particles, allergens (pollen/mold), acids and organic chemicals.

What people may breathe indoors is a whole other issue as many people spend up to 90% of their time indoors where a wide range of gases (radon) and other air pollutants (asbestos) can be concentrated.

These are just a few interesting facts about the air we breathe. To learn more about this or other indoor or outdoor air quality, occupational, environmental, health or safety issues, please visit the websites shown below.

Clark Seif Clark http://www.csceng.com
EMSL Analytical, Inc. http://www.emsl.com
LA Testing http://www.latesting.com
Zimmetry Environmental http://www.zimmetry.com
Healthy Indoors Magazine http://www.iaq.net
VOETS - Verification, Operations and Environmental Testing Services http://www.voets.nyc