Before entering any space that has been sealed, its oxygen level should be tested. What level of oxygen in the space is equal to fresh air?

Correct Answer: Option C — 20.8%

Atmospheric air at sea level contains approximately 20.8% oxygen by volume. When entering enclosed spaces, this baseline is critical for safety. Levels below 19.5% are considered oxygen-deficient, while levels significantly above 20.8% increase fire risks, necessitating strict adherence to confined space entry procedures and gas testing protocols.