The concentration of an airborne substance that an average person can be repeatedly exposed to without
adverse effects. TLVs may be expressed in three ways –
- TLV-TWA-Time weighted average, based on an allowable exposure averaged over a normal 8-hour
workday or 40-hour workweek;
- TLV-STEL-Short-term exposure limit or maximum concentration for a brief specified period of time,
depending on a specific chemical (TWA must still be met); and
- TLV-C- Ceiling Exposure Limit or maximum exposure concentration not to be exceeded under any
circumstances. (TWA must still be met.)