Enriched Air Nitrox diving tables, showing adjusted no-decompression times. The significant aspect of extended no-stop time when using nitrox mixtures is reduced risk in a situation where breathing gas supply is compromised, as the diver can make a direct ascent to the surface with an acceptably low risk of decompression sickness. The exact values of the extended no-stop times vary depending on the decompression model used to derive the padi enriched air manual pdf, but as an approximation, it is based on the partial pressure of nitrogen at the dive depth. The equivalent air depth is used with air decompression tables to calculate decompression obligation and no-stop times.
Nonetheless, there are people in the diving community who insist that they feel reduced narcotic effects at depths breathing nitrox. This may be due to a dissociation of the subjective and behavioural effects of narcosis. DCS and prevent fatigue in both nitrox and air divers. In 2008, a study was published using wet divers at the same depth and confirmed that no statistically significant reduction in reported fatigue is seen.
Further studies with a number of different dive profiles, and also different levels of exertion, would be necessary to fully investigate this issue. For example, there is much better scientific evidence that breathing high-oxygen gases increases exercise tolerance, during aerobic exertion. Though even moderate exertion while breathing from the regulator is a relatively uncommon occurrence in scuba, as divers usually try to minimize it in order to conserve gas, episodes of exertion while regulator-breathing do occasionally occur in sport diving. Examples are surface-swimming a distance to a boat or beach after surfacing, where residual “safety” cylinder gas is often used freely, since the remainder will be wasted anyway when the dive is completed.
It is possible that these so-far un-studied situations have contributed to some of the positive reputation of nitrox. Nitrox50 is used as one of the options in the first stages of therapeutic recompression using the Comex CX 30 table for treatment of vestibular or general decompression sickness. Nitrox is breathed at 30 msw and 24 msw and the ascents from these depths to the next stop. At 18m the gas is switched to oxygen for the rest of the treatment. Nitrox is known by many names: Enriched Air Nitrox, Oxygen Enriched Air, Nitrox, EANx or Safe Air.
When one figure is stated, it refers to the oxygen percentage, not the nitrogen percentage. 32 became shortened as the first figure is redundant. Enriched Air Nitrox” or “EAN”, and “Oxygen Enriched Air” are used to emphasize richer than air mixtures. These two mixtures were first utilized to the depth and oxygen limits for scientific diving designated by NOAA at the time. Considering the complexities and hazards of mixing, handling, analyzing, and using oxygen-enriched air, this name is considered inappropriate by those who consider that it is not inherently “safe”, but merely has decompression advantages. MOD depends on the allowed partial pressure of oxygen, which is related to exposure time and the acceptable risk assumed for central nervous system oxygen toxicity.
2 is often used in closed circuit rebreathers. 4 is recommended by several recreational training agencies for ordinary scuba diving. 5 is allowed for commercial diving in some jurisdictions. Higher values are used by commercial and military divers in special circumstances, often when the diver uses surface supplied breathing apparatus, or for treatment in a chamber, where the airway is relatively secure. 1 hour 14 minutes at this depth. Normally, however, the most oxygen-lean of the diver’s decompression gases would be used for this purpose, since descent time spent reaching a depth where bottom mix is no longer hypoxic is normally small, and the distance between this depth and the MOD of any nitrox decompression gas is likely to be very short, if it occurs at all.
The composition of a nitrox mix can be optimized for a given planned dive profile. This is termed “Best mix”, for the dive, and provides the maximum no-decompression time compatible with acceptable oxygen exposure. This method is very versatile and requires relatively little additional equipment if a suitable compressor is available, but it is labour-intensive, and high partial pressures of oxygen are relatively hazardous. These may be further diluted with air to provide a larger range of mixtures.