Features of a hazardous atmosphere:
(1) places a worker at risk for death, incapacitation, acute illness or becoming unable to escape unaided.
(2) contains one or more of the following:
(2a) flammable material (gas, vapor, mist) > 10% of the lower flammable limit (LFL)
(2b) airborne combustible dust >= lower flammable limit
(2c) oxygen concentration < 19.5% OR > 23.5%
(2d) atmospheric concentration of any toxic substance > permissible exposure limit (see below)
(2e) any other atmospheric condition that is immediately dangerous to life or health
where:
• Airborne dust that obscures vision at a distance <= 5 feet may be assumed to be hazardous.
Lists of toxic substances are published in:
(1) subpart D (Occupational Health and Environmental Controls) of OSHA.1926.55 to 1926.65.
(2) subpart Z (Toxic and Hazardous Substances) of OSHA 1926.1100 to 1926.1153.
