Question

Differentiate between the concepts of ceiling limit, peak limit, and excursion limit.

Answer 1

Ceiling limit: A PEL is usually given as a time-weighted average (TWA), although some are short-term exposure limits (STEL) or ceiling limits. A TWA is the average exposure over a specified period of time, usually a nominal eight hours.

Peak limit: the term is used to refer a level that exceeds the ceiling limit.

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."