What action should be taken if the decompression gas is inaccessible?

Using the back gas to complete decompression is the most appropriate action if the designated decompression gas is inaccessible. Back gas refers to the primary gas supply that divers carry in their tanks for the duration of the dive. When a diver cannot access their specified decompression gas, utilizing back gas allows them to adhere to their planned decompression schedule safely.

This method ensures that the diver remains within safe limits during the ascent and can follow the prescribed ascent rates and stops. It is crucial for avoiding decompression sickness, which can occur if a diver ascends too quickly or omits necessary decompression stops.

Other options, like aborting the dive immediately, might be overly cautious and unnecessary if the diver can safely complete their decompression with available gas. Switching to a nitrox blend may not be viable, especially if the mixture is not suitable for the depths and conditions of the dive, potentially leading to unsafe exposure to oxygen levels. Continuing the dive without assessing gas needs could lead to unsafe conditions, as it does not prioritize the diver's safety and necessary decompression procedures.