Threshold limit value (TLV)
airborne concentrations of substances devised by the American Conference of Government Industrial Hygienists (ACGIH). Representative of conditions under which it is believed that nearly all workers may be exposed day after day with no adverse effects. There are three different types of TLV, TWA, STEL and C.
Note: TLVs are advisory exposure guidelines, not legal standards and are based on evidence from industrial experience and research studies.