Threshold Limit Values (TLVs)

Scope

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.

Regulatory citations

• ACGIH® publishes an annual guide to TLVs

Key definitions

• Threshold limit value (TLV): The average 8-hour occupational exposure limit of a concentration of an airborne substance to which an average person can repeatedly be exposed to without adverse effects.

Summary of requirements

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:

• TLV-TWA (time weighted average), based on an allowable exposure averaged over a normal eight-hour workday or 40-hour workweek.
• TLV-STEL Short-exposure limit or maximum concentration for a brief specified period of time, depending on a specific chemical (TWA must still be met).
• TLV-C Ceiling Exposure Limit or maximum exposure concentration not to be exceeded under any circumstances (TWA must still be met).