What are the three types of purges?

• A. Initial purge; Surface purge; Descent purge
• B. Preliminary purge; Surface purge; Emergency descent purge
• C. Preflight purge; Dive purge; Recovery purge
• D. Primary purge; Secondary purge; Tertiary purge

Answer: (B)

Purges clear moisture and stale gas from the breathing loop so the diver receives clean, breathable gas. The three types are Preliminary purge, Surface purge, and Emergency descent purge.

The Preliminary purge is done on the surface before entry to condition the loop — clearing out water and ensuring the gas in the line is fresh and ready for the dive. The Surface purge is performed at the surface after entering the water to purge any residual gas from the inhalation path, making the first breaths comfortable and ensuring the loop is free of contaminants. The Emergency descent purge is used during an underwater emergency descent to rapidly purge the loop when normal gas flow is compromised, helping to maintain breathable gas delivery during a critical situation.

Other terms used in the choices aren’t standard for this procedure in training, such as “initial” or “dive” purges, or confusing terms like “preflight” (which refers to a pre-dive check, not a purge phase).