Mixed Gas Diving After taking advanced diving courses it is possible to dive with enriched air, also known as nitrox. This air contains 32 percent oxygen in comparison to the 21 percent of the atmosphere and with it comes a reduced amount of nitrogen at only 68 percent. Because the amount of nitrogen is less per breath, the partial pressure of nitrogen at depth is decreased, reducing the chance of decompression sickness and increasing bottom time. The downside of this method is that you must also pay attention to the partial pressure of oxygen in your system which is why further classes are required. Just like with nitrogen, if the partial pressure of oxygen becomes too high it can cause injury, in this case seizures and possible death. However unlike the decompression sickness, this injury is caused by having too much oxygen in your system at one time. This is contrasted with decompression sickness which is caused by not only having too much nitrogen but also coming up too fast allowing the nitrogen to expand in your system. The danger of enriched air can therefore be largely avoided by staying above your max depth to avoid these high oxygen partial pressures. Because of this, using enriched air with conservative diving is largely considered to be a much safer option than diving with normal air. A common misconception around enriched air or nitrox diving is that it allows you do go deeper while being safer. As explained above this is completely false as diving to the depths that can safely be reached for brief periods with normal air is actually quite dangerous with nirtox as the partial pressure of oxygen becomes too high. Instead what people people are thinking of is a different method of mixed gas diving called Trimix. This method uses helium in addition to nitrogen and oxygen in order to lower the effect of nitrogen narcosis (a altered state of mind caused by too much nitrogen inside of your body). This system also further lowers the oxygen to below atmospheric levels to decrease the depths at which the partial pressure of oxygen becomes to high for the body. Because helium is so easily absorbed into the body and the body breathes nitrogen at such depths several decompression stops are required to prevent decompression sickness. This method also commonly utilizes multiple tanks with different types of gas in each that they change depending on their depth. As such, this type of diving is not used by civilian/recreational divers but is instead only used by technical/military divers.