What kind of breathing apparatus recycles the user's exhaled air?

• A. Open-Circuit
• B. Supplied-Air Respirator
• C. Closed-Circuit
• D. Self-Contained Breathing Apparatus

Answer: (C)

Recycling exhaled air means the user breathes air that is captured, cleaned, and reused rather than vented away. In a closed-circuit system, the exhaled breath travels through a CO2 scrubber to remove carbon dioxide, and the oxygen level is replenished as needed, so the air is circulated back to the wearer. This setup lets you operate longer on a finite supply because you’re reusing the same air rather than constantly dumping it to the environment. In contrast, open-circuit setups vent exhaled air to the surroundings and draw in fresh air from the external source, so there is no reuse of the breath. The supplied-air type provides air from an outside source but still doesn’t recycle the user’s exhaled air. While a self-contained breathing apparatus simply means the air is carried with the wearer, the defining factor here is whether the air is recycled inside the system, which is the case with closed-circuit.