According to AirNow, a partnership between EPA and other agencies, "Ozone is a gas that occurs both in the Earth's upper atmosphere and at ground level. Ozone can be 'good' or 'bad' for your health and the environment, depending on its location in the atmosphere...The layer closest to the Earth's surface is the troposphere. Here, ground-level or 'bad' ozone is an air pollutant that is harmful to breathe and it damages crops, trees and other vegetation. It is a main ingredient of urban smog. The troposphere generally extends to a level about 6 miles up, where it meets the second layer, the stratosphere. The stratospheric or 'good' ozone layer extends upward from about 6 to 30 miles and protects life on Earth from the sun's harmful ultraviolet (UV) rays."
See: Good Up High Bad Nearby - What is Ozone?
If you are interested in the relationship between refrigerants, CFCs or Freon and the ozone layer you may be interested in these: Questions and Answers on Alternative Refrigerants.
Here are additional Web sites from other agencies:
- National Oceanic and Atmospheric Administration: Stratospheric Ozone
- United Nations Environment Programme: Ozone Secretariat Exit
You may also be interested in these related Frequently Asked Questions: