Definition(s)
Immediately Dangerous to Life and Health (IDLH)
An atmospheric concentration of any toxic, corrosive, or asphyxiant substance that poses an immediate threat to life or would cause irreversible or delayed adverse health effects or would interfere with an individual’s ability to escape from a dangerous atmosphere. The ACGIH has established 300 ppm or greater of H2S as an IDLH exposure.
Source: API RP 49, Recommended Practice for Drilling and Well Servicing Operations Involving Hydrogen Sulfide, Third Edition, May 2001. Global Standards
Immediately Dangerous to Life and Health
Value defined by OSHA in their HAZWOPER regulation as an atmospheric concentration of any toxic, corrosive or asphyxiating substance that poses an immediate threat to life or would cause irreversible or delayed adverse health effects or would interfere with an individual’s ability to escape from a dangerous atmosphere” (29 CFR 1910.120).
Source: API RP 98, Personal Protective Equipment Selection for Oil Spill Responders, First Edition, August 2013. Global Standards
Immediately Dangerous to Life and Health
The traditional NIOSH definition for published IDLH values is the maximum concentration of an air contaminant from which one could escape within 30 minutes without a respirator and without experiencing any escape-impairing or irreversible health effects. Total loss of respiratory protection in an inert atmosphere can cause virtually immediate impairment and result in rapid asphyxiation. While inert atmospheres are indeed “IDLH” by NIOSH criteria, the hazard is much more immediate and severe.
Source: API Standards 2217A, Guidelines for Safe Work in Inert Confined Spaces in the Petroleum and Petrochemical Industries, Fourth Edition, July 2009. Global Standards