Time-Weighted Average
Time periods which are used for workplace exposure limits (WELs), with two periods of 8-hours (long-term exposure limits - LTELs) and 15-minutes (short-term exposure limits - STELs) being commonly used. “Both the long-term and short-term exposure limits are expressed as airborne concentrations averaged over a specified period of time.” (Source: EH40/2005 Workplace exposure limits, HSE, p.28, https://www.hse.gov.uk/pubns/books/eh40.htm, accessed 10th June 2022)