Excursion Limit definition
Excursion Limit. – means the exposure standards for airborne contaminants are expressed as a TWA concentration over an entire eight–hour working day. However, during this eight–hour averaging period, excursions above the TWA exposure standard are permitted providing these excursions be compensated for by equivalent excursions below the standard during the working day. Because some substances can give rise to acute health effects even after brief exposures to high concentrations, it is evident that excursions above the TWA concentration should be restricted.