STEL 15 : The short-term exposure limit or maximum concentration for a continuous 15 minute exposure (four periods allowed per day, with at least an hour between exposure periods and provided the daily TLV-TWA is not exceeded)
W. A. N Dorland and E. J. Taylor (editors), Glossary of MSDS Terms, Texas A&M University, USA 2001. http://www.bio.tamu.edu/USERS/TONNA/GLOSSARY.HTM, (MSDS - Amer) {631}