Time-Weighted Average-Permissible Exposure Limit

There is no occupational standard for perchlorate but the Occupational Safety and Health Administration regulates perchlorate as a nuisance dust, with an 8h time-weighted average permissible exposure limit of 15mgm. Studies have demonstrated that occupational exposures to perchlorate have not been hazardous to the health of workers at manufacturing plants. 

In the working environment, a principal concern is to ensure that the exposure to elemental phosphorus in air is kept below O.lmg/m, which is the time weighted average permissible exposure limit for workers (TWA, PEL)... 

B. 8-Hour, Time-weighted-average, Permissible Exposure Limit (TWA PEL) ... 

OSHA lists an 8-hour Time-Weighted Average-Permissible Exposure Limit (TWA-PEL) of 50 ppm (35mg/m ) for ammonia. TWA-PEL is the exposure limit that shall not be exceeded by the 8-hour TWA in any 8-hour work shift of a 40-hour workweek [3]. 

OSHA lists an 8-hour Time-Weighted Average-Permissible Exposure Limit (TWA-PEL) of 100 ppm for methyl chloride. TWA-PEL is the exposure limit that shall not be exceeded by the 8-hour TWA in any 8-hour work shift of a 40-hour workweek. In addition, OSHA lists an acceptable ceiling concentration of 200 ppm for methyl chloride. The acceptable ceiling concentration is the exposure limit that shall not be exceeded at any time during an 8-hour shift. Methyl chloride has an exception in that it has an acceptable maximum peak above the acceptable ceiling concentration of 300 ppm for an 8-hour shift as long as the maximum duration is only once for 5 minutes in any hour [3]. 

For butane, the American Conference of Governmental Industrial Hygienists has adopted a threshold limit value of 800 ppm (1900 mg/m ) which is also the eight-hour time-weighted average permissible exposure limit established by the U.S. Occupational Safety and Health Administration. For propane, the TLV adopted by ACGIH and the PEL established by OSH A is 1000 ppm (1800 mg/m ). 

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