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Chapter 43
- 8
NOAA states that the maximum oxygen pressure acceptable is 1.6 ATA. The National Undersea
Research Centre in North Carolina recommends 1.45 ATA. The Swedish authorities have
recommended 1.4 ATA and Dr Richard Vann of the Divers Alert Network has suggested 1.2 ATA.
The US Navy gives a much greater range, and relates it to the duration of the exposures.
The claimed advantages of EANx diving include a probable reduction in decompression sickness
incidence, and a possibility of reduced nitrogen narcosis.
On a theoretical basis, presuming nitrogen pressure as the sole cause of nitrogen narcosis, a 20%
oxygen mixture (air) at 23 metres could be replaced with 36% oxygen at a depth of 30 metres. to
give an equivalent "narcotic effect". Experimental verification for belief in this theory has been
sought, but it was unable to be verified.
A common claim is made that there is less post-dive fatigue with EANx than there is with air. This
has not yet been verified.
LOW RISK NITROX DIVING
NITROX (EANx) REPLACES AIR. SAME EQUIPMENT
(Same Profile as AIR DIVE). RANGE 15 – 40 metres depth.
ADVANTAGES
1. LESS DCS
2. ? LESS NITROGEN NARCOSIS
3. ? LESS POST DIVE FATIGUE
DISADVANTAGES
1. GAS MIXING PROBLEMS
2. LESS MAX DEPTH (O2 TOXICITY)
3. ? DETERIORATION OF DIVE EQUIPMENT
4. ? MORE CO2 RETENTION
It is possible to use EANx to obtain possible advantages, with relatively few disadvantages, under
certain conditions.
In this type of technical diving, the nitrox mixture, usually 32% or 36% oxygen, replaces air, but
the same equipment is used and the same decompression profiles permitted, within the 15 – 40
metre range. Others use 28–40% oxygen, the latter with appropriate depth reduction.
It has been claimed that there is deterioration in the dive equipment by using high oxygen mixtures
but this has not been verified. It is believed that halofluorocarbon O-rings (e.g. Viton) are less