"Occupational exposure limit (OEL)"

means the time weighted average concentration for an eight-hour work day and a 40-hour work week to which nearly all workers may be repeatedly exposed without adverse health effects.

"Occupational exposure limit - ceiling limit (OEL-C)"

means an instantaneous value, which must never be exceeded during any part of the working exposure.

"Occupational exposure limit - short term exposure limit (OEL-STEL)"

means a 15-minute TWA exposure that should not be exceeded at any time during a workday even if the eight-hour TWA is within the OEL-TWA. Exposures above the OEL-TWA up to the STEL should not be longer than 15 minutes and should not occur more than four times per day. There should be at least 60 minutes between successive exposures in this range, An averaging period other than 15 minutes may be recommended when observed biological effects warrant this.

For those substances for which no OEL-STEL have been specified, excluding airborne particulates, a figure of three times the occupational exposure limit is to be used when controlling short-term excursions in exposure.

"Respirable particulates"

means the respirable fraction of airborne particulates.

"Inhalable particulates"

means the inhalable fraction of airborne particulates.