Equivalent air depth

Equivalent Air Depth (EAD) is a concept used in scuba diving, particularly in relation to the use of enriched air nitrox (EANx). The EAD provides a way for divers to estimate the partial pressure of nitrogen (N2) during a dive, which is crucial for avoiding decompression sickness (DCS).

Overview

The EAD is used to simplify dive planning and decompression calculations when diving with EANx. It provides a theoretical depth, which if diving on air, would give the same partial pressure of nitrogen as the actual depth on the EANx mix being used. This allows divers to use air dive tables or air computer settings when diving with EANx, by substituting the EAD for the actual depth.

Calculation

The EAD can be calculated using the following formula:

EAD (in metres) = ((Depth + 10) * Fraction of N2 in the mix) / 0.79 - 10

Where:

• Depth is the actual depth in metres
• Fraction of N2 in the mix is the proportion of nitrogen in the breathing gas (1.0 - fraction of oxygen)
• 0.79 is the proportion of nitrogen in air
• 10 is added and subtracted to convert between absolute and gauge pressure

Applications

The EAD is primarily used in recreational scuba diving, particularly when using EANx. It allows divers to use standard air dive tables or computers, which are widely available and familiar to most divers. This simplifies dive planning and reduces the risk of errors.

However, the EAD does not account for the increased oxygen partial pressure when diving with EANx. Therefore, it should not be used for dives that approach the maximum allowable oxygen partial pressure, or for dives that require decompression stops.

See also

• Decompression (diving)
• Diving cylinder
• Nitrox
• Scuba diving