Here in Malapascua Nitrox is very popular because it allows you to double your bottom time on a 25m dive – exactly the depth we see Thresher Sharks. So there is no confusion about what a great opportunity a nice mix of 32{3c584785206271acba0b48c760be4725f0625fa591b4a52f771ab721d5a102df} can give a diver looking for pelagics.
However there can be a lot of confusion about the benefits or not, and the hazards or not of using nitrox so lets spend a moment to clear those up.
Many people believe using nitrox is much ‘safer’ then air. The logic is that you breathe an oxygen rich mix and therefore absorb less nitrogen into your tissues. We all know that nitrogen turning into bubble form gives us DCS so this must be true? Well maybe not.
By choosing a nitrox blend we change our No Decompression Limit on a dive, for example from 25 minutes to 50 minutes. Take an experienced diver A with good air consumption who will spend 45 minutes on their bottom depth. Had another diver B chosen air they might have stayed 20 minutes, leaving 5 minutes spare on their NDL in both cases.
Ultimately the tissue loading for both divers is going to be pretty similar. Diver A may have had an O2 rich mix but he stayed an additional 20 minutes at depth. So the truth is nitrox is a lot safer . . . if you use it but stick to air profiles.
Secondly the positive benefits of nitrox can easily be cancelled out by the inherent danger of exceeding your partial pressure limit. Nitrox divers need to be experienced enough to monitor their computers and make sure that the partial pressure of oxygen in their tank, and therefore their bodies, never exceeds a 1.4. There is a buffer zone to 1.6 but after that we consider this the zone for potential Oxygen toxicity fits, a guaranteed way to spoil a nice dive and end a life. “Assuming’ every diver is very conscious of this and carefully monitors his depth at all times then Nitrox is safe. We never ‘assume’ anything in diving.
Divers regularly report a positive side effect to using nitrox – less fatigue after diving. Currently this is considered an anecdotal side effect only. Intuitively you might argue that nitrogen loading puts a strain on tissues which on gas and off gas repeatedly over a number of dives. By reducing the amount of on and off gassing your tissues work less resulting in less energy being spent. Maybe. Currently there is no hard proof linking nitrox to energy levels post dive and many think its a pure placebo effect. But placebos can be very powerful so if you believe you feel better after diving nitrox then you do!
One final benefit of nitrox is in dealing with narcosis but of course this is normally limited to divers pushing into the area of Deep Specialties or Technical Diving.
When we teach a Deep Specialty Course here we often discuss using a Best Mix for the dive. This is the optimum nitrox blend for the planned depth. For a 40m dive this would mean we could use a mix of 28{3c584785206271acba0b48c760be4725f0625fa591b4a52f771ab721d5a102df} nitrox (1.4 divided by 5ata = .28) to complete the dive. Instead of a having a partial pressure of nitrogen of 3.95 (.79 x 5ata) which will cause some amount of narcosis in almost all divers we now have a nitrogen partial pressure of 3.6 by using 28{3c584785206271acba0b48c760be4725f0625fa591b4a52f771ab721d5a102df}. Although not huge this small difference can be the difference between muddled decision making and not.
Nitrox may be a quick and easy course to complete but it opens up discussions on many interesting and advanced topics in diving. Nitrox is here to stay and to find our more sign up for our regular nitrox classes or if you are already certified then we can teach you Advanced Nitrox also. For more info just email us on info@evolution.com.ph
