An exposure limit established and enforced by the Occupational Safety and Health Administration (OSHA) which may be expressed as a time-weighted average (TWA) limit, short term exposure limit (STEL) or ceiling exposure limit
Environmental Health and Safety, Glossary, University of Chicago, Illinois, USA 2010. http://safety.uchicago.edu/tools/glossary.shtml, (Ergo - Amer) {753}