STEL is a term used in exposure assessment, occupational health, industrial hygiene and toxicology.
The STEL may be a legal limit in the United States for exposure of an employee to a chemical substance.
The Occupational Safety and Health Administration (U.S. OSHA) has set OSHA-STELs for 1,3-butadiene,[1] benzene[2] and ethylene oxide.
[3] For chemicals, STEL assessments are usually done for 15 minutes and expressed in parts per million (ppm), or sometimes in milligrams per cubic meter (mg/m3).
[4] The American Conference of Governmental Industrial Hygienists publishes a more extensive list of STELs as threshold limit values (TLV-STEL).