suffocating gas
suf·fo·cat·ing gas
suffocating gas
Military medicineA chemical war gas (e.g., chlorine or phosgene) that causes extreme irritation and damage of the respiratory tract and lungs. While such gases were banned by the Geneva Protocol in 1929, they continue to be periodically used in modern warfare.
Occupational medicine
A generic term for gas (e.g., methane, nitrogen, etc.) in a coal mine or other enclosed space which, by replacing normal respiratory gases, causes suffocation.