Editing Permissible exposure limit (section)

{{Short description|Workplace environmental standard}}
The '''permissible exposure limit''' ('''PEL''' or '''OSHA PEL''') is a [[law|legal]] limit in the [[United States]] for exposure of an employee to a [[chemical substance]] or physical agents such as high level noise. Permissible exposure limits were established by the [[Occupational Safety and Health Administration]] (OSHA).  Most of OSHA's PELs were issued shortly after the adoption of the Occupational Safety and Health (OSH) Act in 1970.<ref>{{Cite web|title = OSHA Annotated PELs|url = https://www.osha.gov/dsg/annotated-pels/|website = www.osha.gov|access-date = 2015-10-25}}</ref>

[[regulation of chemicals|Chemical regulation]] is sometimes{{clarify|date=February 2021}} expressed in [[parts per million]] (ppm), but often{{clarify|date=February 2021}} in [[milligram]]s per [[cubic meter]] (mg/m<sup>3</sup>).<ref name=":2">{{Cite web |date=October 29, 2023 |title=Permissible Exposure Limits |url=https://www.osha.gov/annotated-pels |access-date=October 29, 2023 |website=osha.gov/annotated-pels}}</ref> Units of measure for physical agents such as [[noise]] are specific to the agent.

A PEL is usually given as a time-weighted average (TWA), although some are [[short-term exposure limit]]s (STEL) or ceiling limits. A TWA is the average exposure over a specified period, usually a nominal eight hours. This means that for limited periods, a worker may be exposed to concentration excursions higher than the PEL as long as the TWA is not exceeded and any applicable excursion limit is not exceeded. An excursion limit typically means that "...worker exposure levels may exceed 3 times the PEL-TWA for no more than a total of 30 minutes during a workday, and under no circumstances should they exceed 5 times the PEL-TWA, provided that
the PEL-TWA is not exceeded."<ref name="Oregon Rules for Air Contaminants 437-002-0382 (1)c">{{cite web|title=437-002-0382 Oregon Rules for Air Contaminants|url=http://www.cbs.state.or.us/osha/pdf/rules/division_2/div_2.pdf|publisher=Oregon Occupational Safety and Health Division|access-date=30 January 2014|archive-date=4 March 2016|archive-url=https://web.archive.org/web/20160304000403/http://www.cbs.state.or.us/osha/pdf/rules/division_2/div_2.pdf|url-status=dead}}</ref>  Excursion limits are enforced in some states (for example Oregon) and on the federal level for certain contaminants such as asbestos.

A short-term exposure limit is one that addresses the average exposure over a 15-30 minute period of maximum exposure during a single work shift. A ceiling limit is one that may not be exceeded for any time, and is applied to irritants and other materials that have immediate effects.