Safety Definitions
The Definition of Threshold Limit Value (TLV)
Threshold limit value is the maximum airborne concentration of a substance a worker can be exposed to without adverse health effects, as defined by ACGIH.
Threshold limit value is the maximum airborne concentration of a substance a worker can be exposed to without adverse health effects, as defined by ACGIH.
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A recommended airborne exposure limit for a chemical substance, published by the American Conference of Governmental Industrial Hygienists (ACGIH), representing the concentration below which most workers can be exposed repeatedly without adverse health effects. TLVs are guidelines, distinct from OSHA's legally enforceable Permissible Exposure Limits (PELs).
An industrial hygienist references the ACGIH TLV for a solvent used in a paint booth to help evaluate whether current ventilation controls keep worker exposure at a safe level, even though the OSHA PEL for the same substance may differ.
No, TLVs are voluntary guidelines published by ACGIH, while PELs are legally enforceable limits set by OSHA; some PELs are outdated and lower than corresponding TLVs, so many employers use TLVs as an added safety benchmark.
ACGIH reviews and updates TLVs annually as new toxicological research becomes available, which is one reason they are often considered more current than certain OSHA PELs.
ACGIH publishes several types, including Time-Weighted Average (TWA) TLVs for average exposure over a shift, Short-Term Exposure Limits (STEL) for brief high exposures, and Ceiling values that should never be exceeded.
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