Permissible exposure limit (PEL)

OSHA lists its air contaminant PELs in 29 CFR 1910.1000, and some substances, such as lead, asbestos and benzene, have their own detailed standards. Employers must keep exposures at or below the PEL, using engineering controls and work practices first, and respirators only where those cannot reduce exposure enough.

Many of OSHA's general-industry PELs were adopted in the early 1970s and have not been updated for most substances. Because of this, they can be less protective than newer science supports, and other organizations such as NIOSH (Recommended exposure limit (REL)) and ACGIH (Threshold limit value (TLV)) publish recommendations that are often lower. Many companies set stricter internal limits and some regulators in other countries use different values.

PELs usually appear on the SDS in Section 8. They can be expressed in parts per million (Parts per million (ppm)) for gases and vapors or in milligrams per cubic meter for dusts, fumes and mists. A PEL is typically measured as a Time-weighted average (TWA) over a shift, so a brief high exposure may be allowed if the average stays below the limit, unless a Short-term exposure limit (STEL) or Ceiling limit also applies.

A PEL is not a line between safe and unsafe. People vary in sensitivity, and exposure by skin contact or ingestion is not covered by an air limit; check any Skin notation. Staying well below the PEL is good practice.