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

Correct Answer: Option C — threshold limit values

Threshold Limit Values (TLVs) represent the airborne concentration of substances to which nearly all workers can be exposed daily without adverse health effects. These values are essential for establishing safe working environments in confined spaces and ensuring compliance with OSHA and maritime industrial hygiene standards for hazardous gases.