References: NIOSH Pocket Guide to Chemical Hazards, NIOSH, 2005 Definitions: TLV (threshold limit value)-An estimate of the average safe airborne concentration of a substance in representative conditions under which it is believed that nearly all workers may be repeatedly exposed day after day without adverse effect. TLVs are published annually by the American Conference of Governmental Industrial Hygienists (ACGIH). PEL (permissible exposure limit)-The OSHA limits of employee exposure to chemicals; found primarily in 29 CFR 1910.1000, table Z-1. STEL (short term exposure limit)-The maximum concentration for a continuous 15-minute exposure period. Ceiling is the maximum allowable concentration to which an employee may be exposed. IDLH (immediately […]