What is the upper bound of OSHA's acceptable low-oxygen range?

What is the upper bound of OSHA's acceptable low-oxygen range?

• A. 19.5%
• B. 20.9%
• C. 21.0%
• D. 18%

Answer: (B)

Oxygen levels in air are normally about 20.9%. When we talk about a low-oxygen environment, we’re referring to anything below normal air. The highest value that still counts as low-oxygen is essentially the near-normal level itself, which is 20.9%. That’s why this value is the upper bound for the acceptable low-oxygen range. Understanding the others helps see why this is correct: 19.5% is the typical cut-off below which an atmosphere is considered oxygen-deficient and hazardous, so it’s not the upper bound of the low-oxygen range. About 21.0% (or 21%) represents normal air, not low-oxygen. 18% is clearly well below the acceptable range.

Oxygen levels in air are normally about 20.9%. When we talk about a low-oxygen environment, we’re referring to anything below normal air. The highest value that still counts as low-oxygen is essentially the near-normal level itself, which is 20.9%. That’s why this value is the upper bound for the acceptable low-oxygen range.

Understanding the others helps see why this is correct: 19.5% is the typical cut-off below which an atmosphere is considered oxygen-deficient and hazardous, so it’s not the upper bound of the low-oxygen range. About 21.0% (or 21%) represents normal air, not low-oxygen. 18% is clearly well below the acceptable range.