Threshold Limit Values (TLVs) for Chemical Substances and Physical Agents in the Work Environment refer to the average eight-hour occupational exposure limit of a concentration of an airborne substance to which an average person can repeatedly be exposed to without adverse effects. This means that the actual exposure level may sometimes be higher, sometimes lower, but the average must not exceed the TLV.
TLVs are guidelines developed by the American Conference of Governmental Industrial Hygienists (ACGIH®), a private, nonprofit, nongovernmental corporation whose members are industrial hygienists or other occupational health and safety professionals dedicated to promoting health and safety in the workplace. TLVs are not designed to be used as consensus standards and are only one of multiple factors to be considered in evaluating specific workplace situations and conditions. They are intended for use by industrial hygienists in making decisions regarding safe levels of exposure to various chemical and physical agents found in the workplace.
TLVs are one of the four source lists that establish the floor of regulated chemicals under the Hazard Communication Standard (29 CFR 1910.1200, Appendix D), which is cited in the regulations authorized by the Emergency Planning and Community Right To Know Act (EPCRA). They may be expressed in three ways: