Occupational Exposure Limits

Threshold Limit Value (ACGIH) – TLV: Refers to airborne concentrations of substances and represents conditions under which it is believed that nearly all workers may be repeatedly exposed day after day without adverse effect.

Threshold Limit Value: Time-Weighted Average (ACGIH) – TLV-TLW: The time-weighted average concentration for a normal 8-hour work day and a 40-hour work week, to which nearly all workers may be repeatedly exposed, day after day, without adverse effect.

Threshold Limit Value: Short-Term Exposure Limit (ACGIH) – TLV-STEL: The concentration to which workers can be exposed continuously for a short period of time without suffering from (1) irritation, (2) chronic or irreversible tissue damage, or (3) narcosis of a sufficient degree to increase the likelihood of accidental injury, to impair self-rescue, or to materially reduce work efficiency; and provided that the daily TLV-TWA is not exceeded.

Threshold Limit Value: Ceiling (ACGIH) – TLV-C: The concentration that should not be exceeded during any part of the working exposure.

Permissible Exposure Limit (OSHA) – PEL: Same as TLV-TWA

Immediately Dangerous to Life and Health (OSHA) – IDLH: A maximum airborne concentration from which one could escape within 30 minutes without any escape-impairing symptoms or any irreversible health effects.

Recommended Exposure Limit (NIOSH) – REL: Highest allowable airborne concentration that is not expected to injure a worker; expressed as a ceiling limit or time-weighted average for an 8- or 10-hour work day.