In the troposphere, ozone is pollution. In the stratosphere, we find the "good" ozone that protects life on earth from harmful rays from the Sun. Click on image for full size (32K) Courtesy of COMET program

Ozone is made of three oxygen atoms (O₃). You've probably heard of oxygen before -- it's part of the air we breathe. The oxygen that we breathe is made up of two oxygen atoms (O₂). Add another oxygen atom, and you have ozone! When a lot of ozone is around, you would see it as a pale blue gas. Ozone is found in two different layers of the atmosphere, the stratosphere and the troposphere. Where we find ozone in the atmosphere determines whether we consider it to be "good" or "bad"!

In the troposphere, the ground-level or "bad" ozone is an air pollutant that damages human health and plants. It is a key ingredient in smog. In the stratosphere, we find the "good" ozone that protects life on Earth from the harmful effects of the Sun. The simple saying "Good up high and bad near by" sums up ozone in the atmosphere.