Definition - What does Hazardous Atmosphere mean?
A hazardous atmosphere is a dangerous air environment that exposes personnel to the risk of death, incapacitation, injury, acute illness, toxicity or an inability to self-rescue. This type of atmosphere can arise due to flammable gases, large quantities of airborne combustible dust, a lack of oxygen, or any other hazardous atmospheric condition.
Corrosionpedia explains Hazardous Atmosphere
The major causes of a hazardous atmosphere are flammable contents, an oxygen-poor atmosphere and toxins. A waste-, chemical- or toxic-releasing product can give off poisonous gases that contaminate the environment and cause personnel to inhale toxic compounds. Sometimes this goes unnoticed until it is too late; therefore, the atmosphere must be tested before personnel enter a workspace that might contain hazardous chemicals.