What is the “Rule of Thirds” in Nitrox diving?

The "Rule of Thirds" in Nitrox diving is a strategy for effectively managing the dive plan by dividing resources into three equal parts: one-third for the descent, one-third for the bottom time, and one-third for the ascent, including a safety stop. This method is particularly useful for ensuring that divers conserve enough gas for all phases of the dive, which enhances safety and mitigates risks associated with running low on air.

By employing the Rule of Thirds, divers can make more informed decisions. If, for example, a diver spends too much time at the bottom, they may not have enough reserve for a safe ascent. Conversely, if air consumption is high during descent or ascent, then this rule helps anticipate and adjust the dive profile to stay within safe limits.

Other options provided, while relevant in the context of diving, do not specifically relate to the partitioning of dive resources like the Rule of Thirds does. One relates to air consumption calculations, another refers to group dive protocols, and the last pertains to navigation practices, none of which address the prioritization of gas management during various phases of a dive.