Practicality:
1) 40% is a practical limit for recreational sport diving. Most regulators and cylinders can be used without having them oxygen cleaned. There is a consensus amongst the various agencies that gasses with more than 40% O2 should be treated and respected as if it was pure O2.
2) If you are a normal recreational sport diver diving within no-deco limits increasing O2 will merely limit your depth even more while the gas volume in your tank remains the same.
3) Diving with higher O2 percentages not only requires O2 clean equipment but also a much deeper understanding of the dangers and implications of high O2 mixes. Things like CNS and OTUs needs to be well understood.
4) There is also the question of diving ability and skill. A lot of recreational divers with a handful of logged dives and simple Nitrox courses has not necessarily mastered buoyancy and other essential skills. Nitrox 40 or less gives these divers a margin of safety. Unless they dive too deep. That is also one of the main reasons why you also have a max limit of 1.4ppO2. Technical divers will operate between 1.4 and 1.6 depending on the phase of the dive.
5) Nitrox 40 or less also gives you relatively low CNS percentages at the end of dives. That makes repetitive diving very simple from an O2 standpoint. When you increase the O2, planning becomes much more complicated.
Physiology:
1) O2 is a more limiting factor to dive duration and depth at high partial pressures than Nitrogen. Oxygen is also a lot more dangerous under water. When under narcosis you might feel euphoric and do stupid things but an Oxygen Toxicity CNS hit will drown you without much warning.
When you progress to courses like Adv Nitrox with deco you will start using richer mixes than 40%.
At that level of training you will be much more experienced as well as empowered with better equipment and more knowledge.
I highly recommend the Adv Nitrox course or equivalent Tec Rec certification if you are interested in taking your adventure to the next level.
1) 40% is a practical limit for recreational sport diving. Most regulators and cylinders can be used without having them oxygen cleaned. There is a consensus amongst the various agencies that gasses with more than 40% O2 should be treated and respected as if it was pure O2.
2) If you are a normal recreational sport diver diving within no-deco limits increasing O2 will merely limit your depth even more while the gas volume in your tank remains the same.
3) Diving with higher O2 percentages not only requires O2 clean equipment but also a much deeper understanding of the dangers and implications of high O2 mixes. Things like CNS and OTUs needs to be well understood.
4) There is also the question of diving ability and skill. A lot of recreational divers with a handful of logged dives and simple Nitrox courses has not necessarily mastered buoyancy and other essential skills. Nitrox 40 or less gives these divers a margin of safety. Unless they dive too deep. That is also one of the main reasons why you also have a max limit of 1.4ppO2. Technical divers will operate between 1.4 and 1.6 depending on the phase of the dive.
5) Nitrox 40 or less also gives you relatively low CNS percentages at the end of dives. That makes repetitive diving very simple from an O2 standpoint. When you increase the O2, planning becomes much more complicated.
Physiology:
1) O2 is a more limiting factor to dive duration and depth at high partial pressures than Nitrogen. Oxygen is also a lot more dangerous under water. When under narcosis you might feel euphoric and do stupid things but an Oxygen Toxicity CNS hit will drown you without much warning.
When you progress to courses like Adv Nitrox with deco you will start using richer mixes than 40%.
At that level of training you will be much more experienced as well as empowered with better equipment and more knowledge.
I highly recommend the Adv Nitrox course or equivalent Tec Rec certification if you are interested in taking your adventure to the next level.
