The Permissible Exposure Limit (PEL) is a regulatory limit on the amount or concentration of a substance in the air. It is set to protect workers from exposure to hazardous substances in occupational settings. The PEL is usually expressed in parts per million (ppm) or milligrams per cubic meter (mg/m³) and is typically averaged over an 8-hour workday, known as the Time-Weighted Average (TWA).
