eLCOSH : OSHA's Crystaline Silica Rule for .
A concentration of airborne respirable Crystalline Silica of 25 µg/m 3 as calculated over an 8 hour Time Weighted Average (TWA) Crystalline Silica Permissible Exposure Limit (PEL) An airborne concentration of respirable Crystalline Silica in excess of 50 µg/m3 over an 8 hour Time Weighted Average (TWA) Atomic Absorption Spectrophotometer. United States Atomic Absorption Spectrophotometer ...