The average atmospheric concentration of a substance, usually described in parts per million by volume, measured over a specified time period. This latter is usually taken as an 8-hour work day and a 40-hour...

These are set under the Occupational Safety Act. Limits are set for protection of workers against exposure to hazardous workplace substances and conditions. PELs must be both technically and economically...

see Permissible exposure...

Exposure limits specify the maximal allowed exposures for individuals to chemical substances or other obnoxious influences such as noise or radiation. Such limits are usually expressed as environmental concentrations (e.g., 0.1 mg/m3 [milligrams per...