Lab Safety

Exposure Limits

Less Hazardous               More Hazardous

High TLV or PEL               Low TLV or PEL

TLV or PEL (ppm)* Relative Degree of Hazard
Less than 1 Extreme
1 to 10 Extreme to High
10 to 100 High to Moderate
100 to 1000 Moderate
Greater than 1000 Very Low

*ppm = (mg/M3)(24.45)/MW

* Permissible Exposure Limits (PEL) - A legally enforceable exposure limit in air. It represents OSHAs 8-hour weighted average exposure limit for a substance.

* Threshold Limit Value (TLV) - Airborne concentrations of substances that represents conditions under which it is believed that nearly all workers may be exposed day after day with no adverse effect.

Page last modified May 10, 2010