An improper purge will always result in which dive injury?

• A. Hypoxia
• B. Hyperthermia
• C. Decompression sickness
• D. Pulmonary edema

Answer: (A)

In closed-circuit diving, the breathing gas must maintain a safe oxygen partial pressure as you breathe. Purging is a valve operation used to clear the loop, but doing it improperly can disturb the gas balance and reduce the oxygen available to you. If the purge removes oxygen-rich gas or introduces a diluent inappropriately, the effective PO2 drops and you can become hypoxic. Hypoxia reduces the body’s ability to take in and use oxygen, leading to symptoms like confusion, dizziness, or loss of consciousness if it worsens. The other injuries—hyperthermia, decompression sickness, and pulmonary edema—aren’t direct or guaranteed outcomes of an improper purge. The safest, most immediate risk from a faulty purge in a CCR is hypoxia, so correct purge technique and careful monitoring of the gas mix are essential.