What is the recommended depth limit for diving with a 32% Nitrox blend?

The recommended depth limit for diving with a 32% Nitrox blend is based on the maximum partial pressure of oxygen (PPO2) that divers should be exposed to. For recreational diving, it is generally accepted that the maximum PPO2 should not exceed 1.4 ATA (atmospheres absolute) during the course of the dive, which is a safe threshold to prevent oxygen toxicity.

To calculate the maximum depth for a specific Nitrox blend, you can use the PPO2 formula:

PPO2 = (percentage of oxygen in the blend / 100) x (ambient pressure in atmospheres).

At sea level, the ambient pressure is 1 ATA, and the pressure increases by 1 ATA for every 33 feet (10 meters) of depth. For a 32% Nitrox blend, the oxygen percentage is 0.32. Therefore, the maximum depth can be determined by rearranging the formula so that you find the depth where the PPO2 equals 1.4 ATA:

1.4 ATA = (0.32) x (1 + (depth in feet / 33)).

This gives a maximum depth of about 110 feet (33 meters) as the ideal threshold where oxygen toxicity risk is