How to Calculate EAD

When divers ascend from deep water, inert gases dissolved in their blood may form bubbles as the pressure on them drops. To reduce this risk, divers breathe a mixture of gases that has a lower proportion of inert gas than plain air. Divers who use this artificial nitrogen-oxygen mixture can safely brave greater depths. The equivalent air depth (EAD) is the depth that a diver breathing nitrox could reach if he instead breathed air and wanted the same decompression risk.

Instructions

    • 1

      Add 33, which is the depth that produces one bar of pressure, to the diver's depth. For instance, if the diver is 90 feet below the surface: 33 + 90 = 123.

    • 2

      Multiply this answer by the percentage of nitrogen in the nitrox mixture. For instance, if the mixture contains 40 percent oxygen and 60 percent nitrogen: 123 --- 0.6 = 73.8.

    • 3

      Divide this answer by 0.79, which is the fraction of inert gas in air: 73.8 ÷ 0.79 = 93.4.

    • 4

      Subtract 33 from this answer: 93.4 - 33 = 60.4. This is the depth's equivalent air depth, measured in feet.