For a surface interval greater than 7 minutes, what table should be used if two or fewer O2 periods have been completed?

When determining which table to use for a surface interval greater than 7 minutes after completing two or fewer oxygen (O2) periods in an air diving scenario, it is important to reference the correct decompression tables designed specifically for these conditions.

In this case, the correct choice is to use TT-5. This table is intended for dives where a moderate amount of oxygen exposure has occurred, specifically after short surface intervals and limited oxygen periods. It provides the necessary information for safely planning subsequent dives or handling the decompression requirements for divers who have been exposed to O2 for limited durations.

The choice of tables is crucial in ensuring safe dive practices. TT-6, TT-4, or TT-8 would not apply in this scenario since they cater to different sets of conditions regarding surface intervals and O2 exposure. Specifically, TT-6 is typically reserved for longer surface intervals or more extensive oxygen exposure which doesn't align with the less than two O2 periods specified in the question. Thus, TT-5 is tailored for the context provided and ensures proper adherence to safety protocols during air diving operations.