Threshold Limit ValueThreshold Limit Value (TLV) is a registered and reserved term of the American Conference of Governmental Industrial Hygienists (ACGIH). It refers to the maximum average concentration of a hazardous material floating in the workplace to which workers can be exposed during an eight-hour work day and 40-hour workweek, over a working lifetime, without experiencing significant adverse health concerns.refers to the concentration of an airborne substance below which all workers are presumed to be protected while exposed to it day after day for eight-hour periods. It is expressed in parts per million (PPM) of surrounding air for gases and vapors. For fumes, mists, and dusts, it is expressed in terms of milligrams per cubic meter (mg/m3) of surrounding air.
When the concentration of an airborne substance in the working environment is below the TLV, workers are presumed to be safe. In effect, the TLV is the prevailing concentration of a substance in the working environment between safe and dangerous levels.