Nitrox

It is important to distinguish between the terms oxygen compatible and oxygen clean. When modern scuba equipment is delivered it is oxygen compatible in that it has been produced with o-rings and lubricants that are compatible with high FO₂ gas mixtures such as nitrox. Valves and regulators are supplied with Viton® o-rings and lubricated with […]

As previously mentioned, oxygen is an accelerant of combustion and an aggressive oxidizer. All combustion requires three basic elements: Heat, fuel, and oxygen. When all three are present in sufficient quantities, we have a complete fire triangle. When oxygen is in abundance, small quantities of fuel can be induced to burn when heated, and this

Oxygen is an excellent oxidizer and accelerant of combustion. As a result it must be handled and delivered with caution. Scuba cylinders, valves, and regulators must be appropriate for contact with hyperoxic mixtures. When nitrox began to enter the recreational and scientific diving fields there were suggestions that specialized nitrox equipment would be needed to

Mixtures other than air must be properly labeled. The U.S. Department of Transportation (DOT) refers to the labeling specifications of the Compressed Gas Association (CGA), which are covered by CGA Pamphlet C-7, which requires that a compressed gas cylinder bears a neck diamond identifying the cylinder contents. In addition, CGA Pamphlet C-10 specifies that a

Although analysis is a regular function of a nitrox fill station operator, the end user of the gas must always analyze their gas mixture and determine the MOD for the gas mixture being used. Analysis can occur at the fill station or at the dive site, but should be done prior to the final phase

The final method of producing nitrox is the continuous blending method. This method combines medical or aviator grade oxygen with air at 1 ata in a mixing chamber. Air moves through the mixing chamber and oxygen is injected at the top of the chamber. The oxygen combines with the air and the entire contents are

The differential permeability system is similar to the PSA system in that it produces its own oxygen from air. This system differs from PSA in that it uses a differentially permeable membrane to remove nitrogen from air, and the gas flowing from the end of the cylinder is lower in nitrogen and higher in oxygen.

Pressure swing adsorption (PSA) removes nitrogen from air in a molecular sieving operation. The PSA system uses two sieve beds in parallel, one of which is being pressurized and the other depressurized alternately. Low pressure (LP) air is passed through the sieve bed and nitrogen adsorbs to the sieve material, allowing high purity oxygen (up

Partial pressure blending is the least equipment intensive method of producing nitrox but is also the most dangerous, least accurate, and most time consuming production method. In the partial pressure blending method pure oxygen is added directly to a scuba cylinder with a known pressure and FO₂, and then the cylinder is topped off with

There are three basic ways to make nitrox. Each has its advantages and disadvantages and all three methods are in use in a variety of dive shops and facilities. Whatever the method employed to produce nitrox, each end user must analyze their gas cylinders to ensure that the proper mixture has been obtained. A range