John Schroeder, age 99, of Sarosota, Fla., for his question:

WHAT IS FREON?

Freon is a trademark held by the DuPont Company for a group of fluids used in home refrigerators, aerosol sprays and in air conditioners. Freons can also be used as fire extinguising agents and solvents.

Carbon, chlorine and fluorine are the items used in each compound of the Freon group. Together they are called fluorocarbons or chlorofluorocarbons. One of the most widely used Freons has the fancy name of difuorodichloromethane.

Some of the Freons are poisonous, but most of them are not. They have little tendency to corrode metals. Some scientists say that all fluorocarbons released into the atmosphere can harm the earth's protective ozone layer, but the subject is still under study.