After the oxygen passes through the carbon dioxide scrubber canister, where does O2 go?

• A. back into the breathing bag.
• B. to the inhalation hose
• C. to the demand valve
• D. to the exhalation hose

Answer: (A)

In a closed-circuit rebreather, the gas you exhale is scrubbed of CO2 and then recycled back into the breathing loop. The oxygen-enriched gas is returned to the breathing bag (the reservoir that supplies the gas you inhale). From there, it is drawn through the inhalation hose to the mouthpiece as you breathe in. The demand valve opens with inhalation to deliver gas from the bag, and exhaled gas returns to the loop to be scrubbed again. So the oxygen goes back into the breathing bag.