Editing Nitrox (section)

==Production==
{{See also|Gas blending}}
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There are several methods of production:<ref name=dan/><ref name=oxyhackers /><ref name=evil />
* Mixing by partial pressure: a measured pressure of [[oxygen]] is decanted into the cylinder and cylinder is "topped up" with air from the [[diving air compressor]]. 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.
* Pre-mix decanting: the gas supplier provides large cylinders with popular mixes such as 32% and 36%. These may be further diluted with air to provide a larger range of mixtures.
* Mixing by continuous blending: measured quantities of oxygen are introduced to air and mixed with it before it reaches the compressor inlet. Concentration of oxygen is commonly monitored as partial pressure using an [[oxygen cell]]. The compressor and particularly the compressor oil, must be suitable for this service. If the resulting oxygen fraction is less than 40%, the cylinder and valve may not be required to be cleaned for oxygen service. Relatively efficient and quick compared to partial pressure blending, but requires a suitable compressor, and the range of mixes may be limited by the compressor specification.
* Mixing by mass fraction: oxygen and air or nitrogen are added to a cylinder that is accurately weighed until the required mix is achieved. This method requires fairly large and highly accurate scales, otherwise it is similar to partial pressure blending, but insensitive to temperature variations.
* [[Membrane gas separation|Mixing by gas separation]]: a [[nitrogen]] permeable membrane is used to remove some of the nitrogen molecules from air until the required mix is achieved. The resulting low pressure nitrox is then pumped into cylinders by a compressor. <br />A limited range of mixes is possible, but the equipment is quick and easy to operate and relatively safe, as there is never high partial pressure oxygen involved. A supply of clean low-pressure air at a constant temperature is required for consistent results. This may be supplied from a low pressure compressor or a regulated supply from high-pressure storage or compressor. The air must be free of contaminants that could clog the membrane, and at a constant inlet temperature and pressure to produce a consistent delivered partial pressure of oxygen. The air must be of breathing quality, other contaminants must be filtered out independently. The input air pressure is regulated and pressure over the membrane controlled to adjust the product oxygen fraction. CGA Grade D or E air quality is suitable for supply gas, and is commonly heated to a constant inlet temperature. Heating also reduces the chance of high humidity causing wetting of the membrane. In a typical system supply air enters the thousands of hollow fibres of the membrane at one end, and oxygen preferentially permeates the fibre walls, leaving mostly nitrogen at the discharge end, which is vented from the system as waste.<ref name="Nuvair" />
* [[Pressure swing adsorption]] requires relatively complex equipment, otherwise the advantages are similar to membrane separation. PSA is a technology used to separate gases from a mixture under pressure according to the molecular characteristics and affinity for an [[adsorbent]] material of the gases at near-ambient temperatures. Specific adsorbent materials are used as a trap, preferentially adsorbing the target gases at high pressure. The process then swings to low pressure to desorb the adsorbed material and flush the adsorbent container so that it can be reused.