What is the oxygen content range of the air supplied by the SCBA?

What is the oxygen content range of the air supplied by the SCBA?

• A. 23% to 28%
• B. 20% to 25%
• C. 19.5% to 23.5%
• D. 25% to 30%

Answer: (C)

Breathing air supplied by an SCBA must stay within a safe oxygen concentration range to balance enough oxygen for the body with safety from oxygen-related hazards. The standard range is 19.5% to 23.5% by volume. This keeps oxygen levels high enough for metabolism (not dipping below 19.5%) while avoiding oxygen-rich conditions that can increase fire risk and, at high pressures, potential oxygen toxicity (not exceeding 23.5%). Air from SCBA systems is designed to meet this specification, and ambient atmospheric air is about 20.9% oxygen, which falls inside this range. Among the options, the one that aligns with these safety limits is 19.5% to 23.5%. The other ranges extend beyond the safe upper bound (or don’t guarantee the minimum), which is why they’re not correct.

Breathing air supplied by an SCBA must stay within a safe oxygen concentration range to balance enough oxygen for the body with safety from oxygen-related hazards. The standard range is 19.5% to 23.5% by volume. This keeps oxygen levels high enough for metabolism (not dipping below 19.5%) while avoiding oxygen-rich conditions that can increase fire risk and, at high pressures, potential oxygen toxicity (not exceeding 23.5%).

Air from SCBA systems is designed to meet this specification, and ambient atmospheric air is about 20.9% oxygen, which falls inside this range. Among the options, the one that aligns with these safety limits is 19.5% to 23.5%. The other ranges extend beyond the safe upper bound (or don’t guarantee the minimum), which is why they’re not correct.