Threshold Limit Value (TLV)

A threshold limit value refers to the airborne concentration of a substance to which it is believed that nearly all workers may be repeatedly exposed day after day (for 8 hours per day) without harmful effect. Because of individual susceptibility, however, a small percentage of workers may experience discomfort from substances in concentrations at or below the threshold limit. A smaller percentage may be affected more seriously by aggravation of a pre-existing condition orby the development of an occupational illness.