Open Access Articles- Top Results for IDLH


IDLH is an acronym for Immediately Dangerous to Life or Health, and is defined by the US National Institute for Occupational Safety and Health (NIOSH) as exposure to airborne contaminants that is "likely to cause death or immediate or delayed permanent adverse health effects or prevent escape from such an environment." Examples include smoke or other poisonous gases at sufficiently high concentrations. (It is also known as IDHL Immediately Dangerous to Health or Life)

The OSHA regulation (1910.134(b)) defines the term as "an atmosphere that poses an immediate threat to life, would cause irreversible adverse health effects, or would impair an individual's ability to escape from a dangerous atmosphere."[1]

IDLH values are often used to guide the selection of breathing apparatus that are made available to workers or firefighters in specific situations.

The NIOSH definition does not include oxygen deficiency (below 19.5 percent) although atmosphere-supplying breathing apparatus is also required. Examples include high altitudes and unventilated, confined spaces.

The OSHA definition is arguably broad enough to include oxygen-deficient circumstances in the absence of "airborne contaminants," as well as many other chemical, thermal, or pneumatic hazards to life or health (e.g., pure helium, super-cooled or super-heated air, hyperbaric or hypo-baric or submerged chambers, etc.). It also uses the broader term "impair", rather than "prevent", with respect to the ability to escape. For example, blinding but non-toxic smoke could be considered IDLH under the OSHA definition if it would impair the ability to escape a "dangerous" but not life-threatening atmosphere (such as tear gas).

The OSHA definition is part of a legal standard, which is the minimum legal requirement. Users or employers are encouraged to apply proper judgment to avoid taking unnecessary risks, even if the only immediate hazard is "reversible", such as temporary pain, disorientation, nausea, or non-toxic contamination.


The following examples are listed in reference to IDLH values.[2]

Substance IDLH
Carbon dioxide 40000 ppm (4% in a volume of air)
Trifluorobromomethane 40000 ppm
Methyl alcohol 6000 ppm
Ethanol (alcohol found in alcoholic beverages) 3300 ppm
Acetone 2500 ppm
Propane 2100 ppm
Isopropyl alcohol 2000 ppm
Acetaldehyde 2000 ppm
Carbon monoxide 1200 ppm
Octane 1000 ppm
Turpentine 800 ppm
Styrene 700 ppm
Chloroform 500 ppm
Benzene 500 ppm
Toluene 500 ppm
Ammonia 300 ppm
Phenol 250 ppm
Carbon tetrachloride (Halon/Freon) 200 ppm
Sulfur dioxide 100 ppm
Nitric oxide 100 ppm
Hydrogen sulfide 100 ppm
Acetic acid (Vinegar) 50 ppm
Hydrogen cyanide 50 ppm
Phosphine 50 ppm
Nickel tetracarbonyl 30 ppm
Fluorine 25 ppm
Nitric acid 25 ppm
Nitrogen dioxide 20 ppm
Chlorine trifluoride 20 ppm
Formaldehyde 20 ppm
Diborane 15 ppm
Chlorine (used in chemical weapons) 10 ppm
Benzyl chloride (used in chemical weapons)[3] 10 ppm
Dimethyl sulfate (used in chemical weapons)[4] 7 ppm
Ozone 5 ppm
Stibine 5 ppm
Tetramethylsuccinonitrile 5 ppm
Chlorine dioxide 5 ppm
Tetranitromethane 4 ppm
Bromine 3 ppm
Methyl isocyanate 3 ppm
Arsine 3 ppm
Toluene diisocyanate 2.5 ppm
Iodine 2 ppm
Nickel carbonyl 2 ppm
Diazomethane 2 ppm
Selenium hexafluoride 2 ppm
Acrolein 2 ppm
Phosgene (used in chemical weapons) 2 ppm
Chloropicrin (used in chemical weapons) 2 ppm
Hydrogen selenide 1 ppm
Tellurium hexafluoride 1 ppm
Pentaborane 1 ppm
Disulfur decafluoride (about 4 times as poisonous as phosgene) 1 ppm
Sulfur mustard[5] 0.7 ppm
Tabun or Sarin[6] 0.1 ppm
Soman or Cyclosarin[6] 0.05 ppm
VX[6] 0.003 ppm


  1. ^ "Occupational Safety and Health Standards". Occupational Safety & Health Administration. Retrieved 7 July 2012. 
  2. ^ "Chemical Listing and Documentation of Revised IDLH Values". NIOSH Publications and Products. Centers for Disease Control and Prevention. Retrieved 7 July 2012. 
  3. ^
  4. ^
  5. ^ "The Emergency Response Safety and Health Database". National Institute for Occupational Safety and Health (NIOSH). Retrieved 7 July 2012. 
  6. ^ a b c "Nerve Agents". U.S. Department of Labor. Retrieved 7 July 2012. 

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