With surface interval 1-7 minutes after omitting a 20/30 fsw stop, what is the action if no chamber is available?

• A. Return to depth of stop. Multiply stop times by 1.5
• B. Chamber available: Use surface decompression procedure
• C. Observe on surface for 2 hours
• D. Abort decompression and ascend

Answer: (A)

Missing a required decompression stop means you still have excess inert gas that must be off-gassed under pressure. If no chamber is available, the safest course is to descend back to the depth of the missed stop and re-run the decompression, treating the missed segment as if you hadn’t completed it. To account for the additional nitrogen load from the surface interval and the missed stop, multiply each stop time by 1.5. In practice you descend to the original stop depth and perform the planned decompression stops again, using the extended times.

Chamber-based decompression would be used if one were available, but that option isn’t applicable here. Simply waiting on the surface won’t safely resolve the nitrogen loading, and aborting the decompression is not acceptable because you’d be leaving yourself at risk of DCS.