What is the acceptable atmospheric oxygen concentration range?

What is the acceptable atmospheric oxygen concentration range?

• A. 19.5% to 23.0%
• B. 18.0% to 22.0%
• C. 21.0% to 25.0%
• D. 20.0% to 24.0%

Answer: (A)

Maintaining a breathable atmosphere requires keeping oxygen within a safe range. If oxygen drops below 19.5%, people can experience hypoxia and impairment; if it exceeds about 23%, the risk of fire or explosion increases due to more vigorous combustion in oxygen-rich air. The commonly used safe working range is 19.5% to 23.0%, which provides enough oxygen for normal function while limiting fire hazards. The other options either set a lower limit that’s too high above the safe minimum or a upper limit that’s too low, making them unsafe or overly restrictive.

Maintaining a breathable atmosphere requires keeping oxygen within a safe range. If oxygen drops below 19.5%, people can experience hypoxia and impairment; if it exceeds about 23%, the risk of fire or explosion increases due to more vigorous combustion in oxygen-rich air. The commonly used safe working range is 19.5% to 23.0%, which provides enough oxygen for normal function while limiting fire hazards. The other options either set a lower limit that’s too high above the safe minimum or a upper limit that’s too low, making them unsafe or overly restrictive.