Threshold limit value
Exposure limits published annually by the American Conference of Governmental Industrial Hygienists in Threshold Limit Values and Biological Exposure Indices. (TLV® is a registered trademark of the American Conference of Governmental Industrial Hygienists).
API RP 2201, Safe Hot Tapping Practices in the Petroleum & Petrochemical Industries, Fifth Edition, July 2003 (Reaffirmed October 2010), Global Standards
Source:API RP 2009 (2002) Safe welding, cutting and hot work practices in the petroleum and petrochemical industries. Global Standard
Threshold limit value (TLV)
Airborne concentrations of substances representing conditions under which it is believed that nearly all workers may be repeatedly exposed day after day without adverse effects. These value may be expressed as 8-hour time weighted average (TWA), Ceiling Limits, or 15-minute Short-Term Exposure Levels (STEL). Refer to American Conference of Governmental Industrial Hygienists (ACGIH), Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices. “TLV” is a trademarked term of ACGIH.
Source: API RP 49, Recommended Practice for Drilling and Well Servicing Operations Involving Hydrogen Sulfide, Third Edition, May 2001. Global Standards