IDLH
From Wikipedia, the free encyclopedia
An IDLH is a situation Immediately Dangerous to Life and Health, defined by the NIOSH as follows: "that poses a threat of exposure to airborne contaminants when that exposure 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.
IDLH values are often used for the selection of breathing apparatus that must be available to workers or firefighters in a given situation. However, they do not technically include areas with oxygen deficiency (below 19.5 percent) where breathing apparatus is also required (such as at high altitudes or in unventilated, confined spaces).
The OSHA regulation (1910.134(b) defines the term thusly: "Immediately dangerous to life or health (IDLH) means 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."
The OSHA definition is arguably broad enough to include oxygen-deficient circumstances, even if free of any "airborne contaminants," as well as many other chemical, thermal, or pneumatic hazards life or health (e.g., pure helium, super-cooled/heated air, hyper/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 still be considered IDLH if it would impair the ability to escape a "dangerous" but not life-threatening atmosphere (such as tear gas).
As with any standard, this is the minimum legal requirement, and 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.
