R 325.51102 Definitions.

Rule 2. (1) "Ceiling" means the employee's exposure that shall not be exceeded during any part of the workday. If instantaneous monitoring is not feasible, then the ceiling shall be assessed as a 15-minute, time-weighted average exposure that shall not be exceeded during any part of the working day. (2) "Skin designation" means those substances so indicated that have toxic effects due to absorption through an employee's skin. (3) "Short-term exposure limit (STEL)" means the employee's 15-minute, time- weighted average exposure that shall not be exceeded at any time during a workday, unless another time limit is specified in a parenthetical notation below the limit. If another time period is specified, then the time-weighted average exposure over that time limit shall not be exceeded at any time during the workday. (4) "Time-weighted average (TWA)" means the employee's average airborne exposure in any 8-hour workshift of a 40-hour workweek that shall not be exceeded. (5) The terms "substance" and "air contaminant" are equivalent in meaning for purposes of these rules.