Nitrox, or Enriched Air
Created | Updated Apr 12, 2004
Scuba diving is a sport being taken up by thousands of people every year around the world. As technology has developed and Scuba gear is affordable and available, more and more members of the general public have become scuba divers.
Its very common for a scuba diver gearing up for a dive to be approached by a nondiver who points at his scuba cylinder and asks 'How long can you stay down with that?' Since most divers don't have the time or training to teach the well meaning non diver all about the physics of gasses under pressure and diving physiology, they usually respond by sayjng something like ' Oh, about an hour'.
While it's true that divers can only dive as long as there is air in their tanks, its relativly rare for an experienced diver to end a dive simply because his air supply ran low. On many dives, the limiting factor is the amount of Nitrogen being absorbed into the divers bloodstream. Nitrogen is an intert gas that makes up about 79% of the air we breathe. There are mathematical formulas and algorithms that help divers calculate how much Nitrogen is being absorbed into the blood stream at a given depth over a given amount of time. Once a diver goes beyond the time limit for a given depth he or she is obligated to perform a series of 'decompression stops'. These decompression stops require that a diver stop at a certain depth for certain amounts of time and must be rigidly adhered to. Failure to make decompression stops can lead to decompression sickness, sometimes called 'The Bends'. The bends are painful, potentially life threatening and even with tratment may never fully heal. Decompression diving is considered an advanced skill, and should not be attempted by anyone without proper training and equipment. Typically if a recreational diver is in a situation where he or she needs to make decompression stops, they probably made some serious mistakes.
Obviously, the bends are not pleasant, yet divers want to stay underwater for as long as possible without injuring themselvs.
Some divers, physicans and physicists (possibly with the help of some engineers) started thinking one day and said 'Hey, what if we didn't breath so much Nitrogen? I bet we could stay down for a much longer time! So they grabbed a diver, gave him a cylinder filled with pure oxygen and threw him in the water. As he descended past 20 feet he had a seizure and drown. Thus the diving community learned about oxygen toxicicty. (A condition that is essentially an Oxygen Overdose, where the gas actually begins to act almost as a Neurotoxin. This occurs when you have about 8 times the level of Oxygen in your bloodstream that you normally should.) Once things settled down, someone came up with the idea of adding just a little extra oxygen to a divers air, thereby eliminating some nitorgen and thus allowing divers to stay down longer without having to make decompression stops. However, it decreases the maximum allowable depth before oxygen toxicity sets in. The practice of Enriched Air Nitrox diving was born.
Enriched Air Nitrox is sometimes simply called Nitrox or EANx or even SafeAir. Because age, weight and physical condition can increase the risk of the bends Nitrox has also been called the 'fat and over 40 gas'. It's simply regualr air that has some extra oxygen added. To understand this a bit better lets accept that the air we breath is about 79% Nitrogen and 21% Oxygen. (Its a bit more precise than that, but rounding makes the math a little easier.) One of the most common varieties of Nitrox is called Nitrox I or Ean32. This means that the air in a SCUBA tank contains 32% Oxygen, and Nitrogen now occupies about 68% of the tanks total volume. Other common blends are EAN36 (Nitrox II) or EAN40. More than 40% concentrations require more training and equipment that has been Oxygen Cleaned. This means that the equipment is free of any oils or other chemicals that could react with the Oxygen under pressure and cause an explosion.
When a diver adds extra oxygen to their SCUBA tank they automatically start limiting the depth to which they can safely dive, because of the problem of Oxygen toxicity. If you are diving Nitrox, the person (blender) who filled your SCUBA tank should clearly label the tank with the gas mixtue and the Maximum Operating Depth or MOD. The math to figure the correct MOD for any given gas mixture is straight forward, but a simple way to explain it is this: The greater the concentration of Oxygen in your tank the shallower your depth must be.
Although this researcher is unaware of any scientific reseach to support this claim, many Nitrox divers claim that becuase they are breathing more oxygen at higher concentrations than normal during a dive they feel less fatigued at the end of a day of diving than if they had simply been breathing compressed air.
Its very common for a scuba diver gearing up for a dive to be approached by a nondiver who points at his scuba cylinder and asks 'How long can you stay down with that?' Since most divers don't have the time or training to teach the well meaning non diver all about the physics of gasses under pressure and diving physiology, they usually respond by sayjng something like ' Oh, about an hour'.
While it's true that divers can only dive as long as there is air in their tanks, its relativly rare for an experienced diver to end a dive simply because his air supply ran low. On many dives, the limiting factor is the amount of Nitrogen being absorbed into the divers bloodstream. Nitrogen is an intert gas that makes up about 79% of the air we breathe. There are mathematical formulas and algorithms that help divers calculate how much Nitrogen is being absorbed into the blood stream at a given depth over a given amount of time. Once a diver goes beyond the time limit for a given depth he or she is obligated to perform a series of 'decompression stops'. These decompression stops require that a diver stop at a certain depth for certain amounts of time and must be rigidly adhered to. Failure to make decompression stops can lead to decompression sickness, sometimes called 'The Bends'. The bends are painful, potentially life threatening and even with tratment may never fully heal. Decompression diving is considered an advanced skill, and should not be attempted by anyone without proper training and equipment. Typically if a recreational diver is in a situation where he or she needs to make decompression stops, they probably made some serious mistakes.
Obviously, the bends are not pleasant, yet divers want to stay underwater for as long as possible without injuring themselvs.
Some divers, physicans and physicists (possibly with the help of some engineers) started thinking one day and said 'Hey, what if we didn't breath so much Nitrogen? I bet we could stay down for a much longer time! So they grabbed a diver, gave him a cylinder filled with pure oxygen and threw him in the water. As he descended past 20 feet he had a seizure and drown. Thus the diving community learned about oxygen toxicicty. (A condition that is essentially an Oxygen Overdose, where the gas actually begins to act almost as a Neurotoxin. This occurs when you have about 8 times the level of Oxygen in your bloodstream that you normally should.) Once things settled down, someone came up with the idea of adding just a little extra oxygen to a divers air, thereby eliminating some nitorgen and thus allowing divers to stay down longer without having to make decompression stops. However, it decreases the maximum allowable depth before oxygen toxicity sets in. The practice of Enriched Air Nitrox diving was born.
Enriched Air Nitrox is sometimes simply called Nitrox or EANx or even SafeAir. Because age, weight and physical condition can increase the risk of the bends Nitrox has also been called the 'fat and over 40 gas'. It's simply regualr air that has some extra oxygen added. To understand this a bit better lets accept that the air we breath is about 79% Nitrogen and 21% Oxygen. (Its a bit more precise than that, but rounding makes the math a little easier.) One of the most common varieties of Nitrox is called Nitrox I or Ean32. This means that the air in a SCUBA tank contains 32% Oxygen, and Nitrogen now occupies about 68% of the tanks total volume. Other common blends are EAN36 (Nitrox II) or EAN40. More than 40% concentrations require more training and equipment that has been Oxygen Cleaned. This means that the equipment is free of any oils or other chemicals that could react with the Oxygen under pressure and cause an explosion.
When a diver adds extra oxygen to their SCUBA tank they automatically start limiting the depth to which they can safely dive, because of the problem of Oxygen toxicity. If you are diving Nitrox, the person (blender) who filled your SCUBA tank should clearly label the tank with the gas mixtue and the Maximum Operating Depth or MOD. The math to figure the correct MOD for any given gas mixture is straight forward, but a simple way to explain it is this: The greater the concentration of Oxygen in your tank the shallower your depth must be.
Although this researcher is unaware of any scientific reseach to support this claim, many Nitrox divers claim that becuase they are breathing more oxygen at higher concentrations than normal during a dive they feel less fatigued at the end of a day of diving than if they had simply been breathing compressed air.
