Is it appropriate to forcefully blow out of the mouthpiece?

• A. Yes
• B. No
• C. Only during pre-dive checks
• D. Only if instructed by a supervisor

Answer: (B)

In a closed-circuit or regulator-breathing setup, the mouthpiece is part of the breathing loop, so exhalation should be smooth and controlled. Forcing air out of the mouthpiece can create sudden backpressure and disturbance in the loop, which can lead to a regulator free-flow, an uncomfortable bite or mouthpiece displacement, or water entering the mouth or system if the mouthpiece is flooded. It can also provoke coughing or aspiration if water is present.

So the safe, correct approach is to breathe normally and calmly. If you need to clear water or moisture, use the equipment’s proper clearing procedure (purge or other approved method) rather than blowing forcefully.

The other options imply that forceful blowing is acceptable in some situations, but that’s not the safe practice at any time, including pre-dive checks or under supervision.