169. The airborne concentrations of substances (such as hydrogen sulfide) under which nearly all workers may be repeatedly exposed without adverse effects are called __________.

Threshold limit values (TLVs) are defined as airborne concentrations to which nearly all workers can be repeatedly exposed without adverse health effects. TLVs are guidelines established by ACGIH and represent standardized occupational exposure limits, unlike the generic terms 'exposure limits' or 'concentration limits'.