What is the most important setting that should be configured on a Nitrox computer before each dive?

The most important setting to configure on a Nitrox computer before each dive is the FO2, which stands for the Fraction of Oxygen. This setting indicates the percentage of oxygen in the breathing gas being used, which is crucial for assessing both the safety of the dive profile and the potential risks associated with oxygen exposure.

Having the correct FO2 ensures that the dive computer reads and calculates important parameters such as no-decompression limits, decompression stops, and overall dive time based on the specific mixing of the gases being utilized. Different percentages of oxygen can significantly alter the physiological effects of the dive, and mistakes in setting this value could lead to serious risks like oxygen toxicity or inadequate decompression from higher percentages of oxygen at greater depths.

The other parameters, while important, do not take precedence over accurately setting the FO2. MOD (Maximum Operating Depth) relates to the maximum depth allowed for a particular oxygen percentage but is derived from the FO2 setting. DNF (Do Not Exceed) is typically a guideline dependent on the FO2 level and dive plan. O2% is often used interchangeably with FO2, but FO2 specifically focuses on the operational configuration necessary for safe diving. Thus, ensuring the FO2 is set correctly is critical for a safe