Your Safer Source for Science

Since 1977

Address P.O. Box 219 Batavia, IL 60510
Phone 800-452-1261
Fax 866-452-1436

When are vapors harmful to you and your students? Threshold Limit Values (TLV) and Permissible Exposure Limits (PEL) refer to the levels of a chemical above which a person should avoid repeated and prolonged exposure.