text: American Nitrox Divers International (ANDI) uses the term "SafeAir", which they define as any oxygen-enriched air mixture with O2 concentrations between 22% and 50% that meet their gas quality and handling specifications, and specifically claim that these mixtures are safer than normally produced breathing air for the end user not envolved to the mix production which. 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.
  The constituent gas percentages are what the gas blender aims for, but the final actual mix may vary from the specification, and so a small flow of gas from the cylinder must be measured with an oxygen analyzer, before the cylinder is used underwater.
  MOD
  Maximum Operating Depth (MOD) is the maximum safe depth at which a given nitrox mixture can be used. 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. Acceptable maximum ppO2 varies depending on the application:
  1.2 is often used in closed circuit rebreathers.
  1.4 is recommended by several recreational training agencies for ordinary scuba diving.
  1.5 is allowed for commercial diving in some jurisdictions.
  1.6 is allowed for technical diving decompression stops, and is the recommended maximum according to NOAA
  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.
  Equipment