What are the benefits of breathing Nitrox during recreational dives?

Nitrox is mainly used in scuba diving to reduce the proportion of nitrogen in the breathing gas mixture. Reducing the proportion of nitrogen by increasing the proportion of oxygen reduces the risk of decompression sickness, allowing extended dive times without increasing the need for decompression stops with shorter surface time intervals. Nitrox is not a safer gas than compressed air in all respects: although its use reduces the risk of decompression sickness, it increases the risk of oxygen toxicity. It is commonly believed that breathing nitrox can reduce the effects of nitrogen narcosis, but this has not been fully studied. In fact, there is some suggestion that oxygen may also have some narcotic properties under pressure; thus one should not expect a reduction in narcotic effects due only to the use of nitrox. There is anecdotal evidence that the use of nitrox reduces post-dive fatigue, particularly in older divers, but there have been no studies conducted to either confirm or refute this.

How will using Nitrox blending systems affect my dive shop business?

With the Nitrox blending system your shop will be able to offer Nitrox to recreational divers and trimix mixtures to professional and technical divers. The blending system will open up a larger customer base for tank fills as well as expand the customer base for training classes and the purchase of Nitrox accessories. Unlike Nitrox done without a blending system, the tanks can be filled and return to divers just as quickly as traditional air fills. There is no need for lead time or tank rolling.

How is continuous nitrox blending achieved?

We start by regulating pure low pressure oxygen into several feet of loosely coiled compatible metal tubing. Air and oxygen flow into the intake of a high-pressure air compressor after they are mixed. A small amount of this gas mixture flows through an inline oxygen analyzer so that the gas blender can calibrate the flow regulator to obtain the correct rate to produce the desired oxygen percentage at the compressor output. The operator can either continuously blend nitrox into a single scuba cylinder, a large storage cylinder, or a storage bank. By filling a storage bank with an oxygen-rich mixture(e.g. EAN32 or EAN 36),the option of premix blending may save time over continuously blending into a single scuba cylinder. In either case, the advantages are no hydrocarbons and a high quality breathing gas.

Which is better partial pressure blending or continuous?

Partial pressure blending is the least expensive technique, but it is the most hazardous. With a continuous system you don't handle pure oxygen and you don't need any O2 clean equipment.

What is the partial pressure blending process?

It begins by slowly and carefully adding a very specific amount of Grade A oxygen into an empty high-pressure cylinder that is prepared for oxygen service. Very specific precautions are taken to make sure no accidents occur. The fill rate does not exceed 60 psi per minute and the cylinder never becomes warm to the touch. Also, the oxygen supply line must have an oxygen regulator, slow operating needle valve and inline restrictors. Upon reaching the correct oxygen pressure , we let the reading stabilize on the master gauge. If the pressure is correct, finish filling the cylinder to its service pressure with dry hydrocarbon-free air. The fill rate for adding H-C free air should not exceed 400 psi per minute.

It is based on Dalton’s law where: p = PG1 + PG2 + PG3 + …PGn. “PG” represents the partial pressure of a single gas within a mixture. The raised numbers refer to individual gasses within the mix, “PGn ” represents the infinite number of gasses that could be in a mixture, and “P” is absolute pressure. Dalton’s law states, “the total pressure exerted by a gaseous mixture is equal to the sum of the partial pressures of the gasses that make up the mixture. Translation- the total is equal to the sum of the parts. 

What is Heliair?

Sometimes termed “poor mix”, Helair is the partial pressure blending process only involves adding pure helium to an empty cylinder and then complete filling with air. Not having to add oxygen reduces part of the fill cost and it avoids the dangers of working with pure oxygen. The disadvantage is Helair will always have an oxygen count less than 21%. to avoid hypoxia (insufficient tissue oxygenation), if it is below 16%, a travel mix with a higher Fo2 becomes necessary) A diver breathes a travel mix to descend to the depth where the Helair mixture is no longer hypoxic and is safe to breath. During the ascent, they switch back to the travel mix at the same depth to again avoid hypoxia. Often the travel mix is an oxygen-rich nitrox that they will use during staged decompression