Which combination represents a safe atmosphere reading during fit testing?

Which combination represents a safe atmosphere reading during fit testing?

• A. CO less than 35 ppm and O2 greater than 19.5%
• B. CO less than 50 ppm and O2 greater than 21%
• C. CO less than 10 ppm and O2 greater than 19%
• D. CO less than 35 ppm and O2 greater than 23%

Answer: (A)

During fit testing, the air in the test environment must be safe to breathe. The key safety checks are that the oxygen level is not too low (to prevent hypoxia) and the carbon monoxide level is not high (to avoid toxicity and interference with the test). A commonly accepted safe combination is oxygen above 19.5% and carbon monoxide below 35 ppm. This meets the minimum breathable air requirement while staying well below a toxic CO exposure level. The other options either exceed the CO limit (making it unsafe), or do not guarantee the minimum oxygen level, or suggest an oxygen level beyond typical safe handling during testing. Therefore, the combination with CO under 35 ppm and O2 over 19.5% is the safest and correct choice.

During fit testing, the air in the test environment must be safe to breathe. The key safety checks are that the oxygen level is not too low (to prevent hypoxia) and the carbon monoxide level is not high (to avoid toxicity and interference with the test). A commonly accepted safe combination is oxygen above 19.5% and carbon monoxide below 35 ppm. This meets the minimum breathable air requirement while staying well below a toxic CO exposure level. The other options either exceed the CO limit (making it unsafe), or do not guarantee the minimum oxygen level, or suggest an oxygen level beyond typical safe handling during testing. Therefore, the combination with CO under 35 ppm and O2 over 19.5% is the safest and correct choice.