Recommendation by U.S. OSHA for a time-weighted average concentration that must not be exceeded during any \(\pu{8\!\mbox{-}h}\) work shift of a \(\pu{40\!\mbox{-}h}\) working week.
Source: PAC, 2007, 79, 1153. (Glossary of terms used in toxicology, 2nd edition (IUPAC Recommendations 2007)) on page 1280 [Terms] [Paper]