In case O2 cannot be corrected and a chamber is available, what is the first action?

Initiating Sur 'D', or surface decompression, is the appropriate first action when faced with a situation where oxygen levels cannot be corrected, provided that a chamber is available. This protocol is crucial in ensuring the safety of divers who may be suffering from complications related to oxygen toxicity or other physiological issues due to improper gas mixtures or environments.

Sur 'D' allows divers to manage their ascent in a controlled manner while still receiving therapeutic benefits similar to those offered in a hyperbaric chamber. The process entails surfacing at a predetermined rate while allowing the diver to decompress safely. This minimizes the risk of decompression sickness and other dive-related health complications that could arise if the incorrect gas mixture continues to be utilized.

In contrast, continuing to dive on air or surfacing to recover could expose divers to serious health risks due to inadequate oxygen levels. Administering first aid is important in various diving emergencies; however, it does not address the fundamental issue at hand, which is the inability to correct the oxygen levels in the diving environment. Therefore, the best course of action focuses on the immediate and safe management of the diver's condition through Sur 'D'.