Airborne concentrations of substances under which it is believed that nearly all workers may be exposed day after day with no adverse effect. TLV’s are advisory exposure guidelines, not legal
standards, that are based on industrial experience and studies.
There are three different types of TLV’s:
– Time Weighted Average (TLV-TWA) — the airborne concentrations of a toxic substance averaged over an 8 hour period, usually expressed in parts per million (ppm).
– Short Term Exposure Limit (TLV-STEL) — the airborne concentration of a toxic substance averaged over any 15 minute period, usually expressed in parts per million (ppm).
– Ceiling (TLV-C) – The concentration that should not be exceeded during any part of the working exposure.