http://www.epa.gov/oar/oaqps/gooduphigh/
Office of Air and Radiation, U.S. Environmental Protection Agency
This consumer health information brochure answers questions about ozone gas, its benefits and dangers. It describes "good" ozone and "bad" ozone and discusses what is being done about depletion of "good" ozone and the introduction into the atmosphere of increasing levels of "bad" ozone.