Which oxygen concentration is considered dangerous?

Which oxygen concentration is considered dangerous?

• A. Below 7%
• B. Above 27%
• C. Above 20%
• D. Exactly 7%

Answer: (A)

Oxygen deficiency is the hazard being tested. We normally breathe air with about 21% oxygen, and as the level drops, the body can’t get enough oxygen to its tissues. At extremely low levels—around seven percent—the lack of oxygen becomes acute, causing rapid loss of consciousness and can be life-threatening if rescue or ventilation isn’t immediate. That severe deficiency is what makes this concentration dangerous. The other options aren’t as clearly dangerous in typical breathing scenarios: slightly higher than normal oxygen is a different kind of risk (fire hazard or oxygen toxicity in specific settings) but not the immediate danger of hypoxia; around normal breathing levels is not dangerous; and while seven percent itself is dangerous, the key idea being tested is the extraordinarily low concentration that poses an immediate, severe risk.

Oxygen deficiency is the hazard being tested. We normally breathe air with about 21% oxygen, and as the level drops, the body can’t get enough oxygen to its tissues. At extremely low levels—around seven percent—the lack of oxygen becomes acute, causing rapid loss of consciousness and can be life-threatening if rescue or ventilation isn’t immediate. That severe deficiency is what makes this concentration dangerous.

The other options aren’t as clearly dangerous in typical breathing scenarios: slightly higher than normal oxygen is a different kind of risk (fire hazard or oxygen toxicity in specific settings) but not the immediate danger of hypoxia; around normal breathing levels is not dangerous; and while seven percent itself is dangerous, the key idea being tested is the extraordinarily low concentration that poses an immediate, severe risk.