What is the recommended maximum depth for diving with EANx 36?

The recommended maximum depth for diving with EANx 36, or enriched air nitrox with 36% oxygen, is primarily based on the need to manage the risk of oxygen toxicity. The key factor in determining the maximum operational depth when using enriched air is the partial pressure of oxygen (PPO2) that divers are exposed to during a dive.

For EANx 36, the safe maximum partial pressure of oxygen is generally set at 1.4 ATA (atmospheres absolute) for recreational diving. At depths beyond this, the risk of oxygen toxicity increases significantly. The calculation for determining the maximum safe depth involves using the formula:

PPO2 = (percentage of oxygen in the mix/100) x (ambient pressure in ATA).

At 30 meters (approximately 100 feet), the total ambient pressure is about 4 ATA (1 ATA at the surface plus 3 ATA due to water pressure). When we apply the formula for EANx 36:

PPO2 at 30 meters = (36/100) x 4 = 1.44 ATA, which is just above the maximum safe limit of 1.4 ATA. However, often for conservative practices and dive planning, many divers consider 30