View Full Version : Benefits of Nitrox?
...Continued from the other thread, which was about teaching it to OD and SD.
Matt,
The paper I read was published in the UHMS journal: http://archive.rubicon-foundation.org/dspace/handle/123456789/3805 (free scubcription required to download the pdfs). Although I wasn't too impressed by the study. IIRC the sample size was very small.
On the benefits of Nitrox, then have you seen this: http://www.kitfondle.co.uk/images/nitrox/
Personally I thing Nitrox is a good thing for Ocean Divers. Not because it's better than air if they stick to the plan, but because there's less chance of DCI if they lose it and have a rapid ascent.
Janos
whilst ive been doing my dissertation ive been looking very closly into the physics and maths behind diving and (no offence ment if you already know it im just showing of a touch) the main advantage of nitrox is that it has a reduced partial pressure of Nitrogen avalible to enter the system, infact breathing it at the surface reduces your nitrogen loading prior to adive.
its main advantage however comes from not the reduction in total quanity of gas but the reduction in the ammount which can be onngassed into the tissue groups b reducing the Parital pressure differntial avalible for the tissues to take on. this reduces the ammount which is ongassed in a half time and, seeing as most dives are so much shorter than some tissue half times this results in an a reduction in the partial pressure increase the tisses can take on.
resulting therfore in less inert gas in the body thus safer
that said i dont personaly think it should be part of the qulaification training it should be a progression for experiance after training is complete and more info into the science behind it is essential.
Michael Purcell
20-03-2007, 03:02
Does your opinion hold for Nitrox 20.9% ?
God's Nitrox is just another blend...:D
John Bantin
20-03-2007, 08:02
As many would-be divers start training expecting to be breathing from an oxygen tank (thanks to the media) what difference would it make to tell them they were breathing compressed Nitrox (say Nitrox32) instead of explaining they would be breathing compressed air? I can foresee the day when Nitrox32 will be the standard gas for all sub-40m (shallower than) leisure divers.
[QUOTE=paul_c]whilst ive been doing my dissertation ive been looking very closly into the physics and maths behind diving and (no offence ment if you already know it im just showing of a touch)
resulting therfore in less inert gas in the body thus safer
[QUOTE]
The way I dive nitrox it does not end up with "less inert gas in the body" as I stay down longer ! This is the way many of us dive the gas (using the fact the ppN2 is lower so diving a END)
Therefore I see it having no safety benefit due to ppno2. As it raises ones O2 exposure more than air by a tad, perhaps it is reducing safety by a miniscule amount ;-)
Whether END has justification in fact rather than yet another theory, who knows ? (this is something that is no discussed much, just accepted !)
Tony
www.twiki.co.uk
I can foresee the day when Nitrox32 will be the standard gas for all sub-40m (shallower than) leisure divers.
I think in some places it already is, last year in the Red Sea you got 32% unless you told them otherwise
The way I dive nitrox it does not end up with "less inert gas in the body" as I stay down longer ! This is the way many of us dive the gas (using the fact the ppN2 is lower so diving a END)
Therefore I see it having no safety benefit due to ppno2. As it raises ones O2 exposure more than air by a tad, perhaps it is reducing safety by a miniscule amount ;-)
Whether END has justification in fact rather than yet another theory, who knows ? (this is something that is no discussed much, just accepted !)
I think END there is a hell of a lot of discussion about, a significant number of people think O2 is just as narcotic as N2 so using END to judge nitrox is seriously flawed.
EAD is another matter entirely, we do pretty much just accept it as fact with no widely reported evidence to confirm it. Does anyone know of any research to support the theory?
I think END there is a hell of a lot of discussion about, a significant number of people think O2 is just as narcotic as N2 so using END to judge nitrox is seriously flawed.
EAD is another matter entirely, we do pretty much just accept it as fact with no widely reported evidence to confirm it. Does anyone know of any research to support the theory?
When I mean't END is just Equivalent Nitrogen Depth i.e. ppN2
a 30 % nitrox at 30m can be treated as 40% at 20m for deco as they have the same ppN2
I used the term incorrecty as it is normally used to compare back to AIR ppN2.
I've never seen any proof of EAD. its just "common sense ;-)" the same Common sense that would lead the general public in thinking that double the wind speed = double the force (and they would be wrong !)
Tony
ps Even Jplan has "treat O2 as narcotic" as an option !
Personally I thing Nitrox is a good thing for Ocean Divers. Not because it's better than air if they stick to the plan, but because there's less chance of DCI if they lose it and have a rapid ascent.Hi Janos. Let's do the quick one first. It could take me a while to type up the deep stops thing.
Anyhow. I mainly agree with you although I still think the best way to protect an OD from the dangers of rapid ascents is to encourage them to dive shallow and often. Whether the current OD qualification depth and limitations, as to whom and in what circumstance they can dive, helps to achieve that is another thread entirely ;)
The main benefit I see in giving Nitrox to ODs is that it will finally de-mystify the gas. At this level Nitrox is just another flavour of air more suited to shallow diving. The main (only) thing we need to teach is Know what you are breathing. Everything else that get's spouted as reasons why Nitrox is too complicated and can't possibly be given to ODs is about as relevant to an OD as the 50m air MOD. It is just a shame that counter diffusion appears to be another excuse to make Nitrox complicated for no good reason.
So in BSAC fashion we will introduce Nitrox in OD, refresh and progress at SD and that is what I call BSAC making a real difference within UK diving. Who knows the increased demand might even persuade the industry to do it's bit and encourage Nitrox diving by lowering the costs (see I am an optimist really).
a 30 % nitrox at 30m can be treated as 40% at 20m for deco as they have the same ppN2Putting it the other way breathing 32% at 20m is (allegedly) equivalent to breathing air at 15m for decompression planning purposes. So an OD breathing 32% is unlikely to get anywhere near the no-decompression limit.
When divers progress deeper, after qualifying as SDs, Nitrox can be used to extend the no-stop time (as you use it). The air decompression ceiling comes down relatively quickly deeper than 25m which can take a little getting used to when previously dives were limited by gas supply. Notrox for SDs should give them one less thing to worry about as they get used to the increased gas consumption and lower light levels that come with progressively deeper diving. In the past SDs tended to defer Nitrox training until they were confident of passing the midwater assessments in the Combined course - which is too late.
I used the term incorrecty as it is normally used to compare back to AIR ppN2.END (Equivalent Narcotic Depth) is generally used to describe the Narcotic potency of a Trimix compared to air. EAD (Effective Air Depth) is generally used to describe the decompression characteristics of Nitrox compared to air. The calculations are one and the same. Distinguisihing the two is (probably) worthwhile to stop the Nitrox is less narcotic myth spreading any further than it has already.
I've never seen any proof of EAD. its just "common sense ;-)" the same Common sense that would lead the general public in thinking that double the wind speed = double the force (and they would be wrong !)I suspect that if I were to train in whatever discipline you are referring to Tony the physical law which results in double wind speed <> double force would be taught to me. The same can be said of EAD in so far as it is based on gas laws that were accepted hundreds of years ago (Graham, Lussac, Fick).
Noteably Dr Tom Hennessy disputes the accuracy of the EAD principle, presumably on physiological grounds. Whilst I have the greatest respect for Dr Hennessy, as one of the few that really understands the marriage of physics and physiology within decompression science, he unfortunately refuses to share his work. In the absence of an explanation I am happy to use EAD to plan and complete Nitrox dives; as it seems is every other user of a Nitrox capable computer.
I suspect that if I were to train in whatever discipline you are referring to Tony the physical law which results in double wind speed <> double force would be taught to me. The same can be said of EAD in so far as it is based on gas laws that were accepted hundreds of years ago (Graham, Lussac, Fick). .
I think you missed my point here.
Most people except EAD because it makes sense (common sense ?) it is very simplistic maths. Just because it is simple does not mean it works.
i.e. Newtonian mechanics is ok F=ma (simple) , but as things get faster they are not ok and are not longer a first order equations (thanks einstein)
The knowledge of gas equations are old (I even studied at Uni for a laugh) but how that ppN" affects our body is not known still. If it was known we would have a model for deco (like a model for gas equations) rather than a the plethera we have.
Pehaps END does require a slight change, perhaps it is an equation where absolute pressure is a variable as well ?
Perhaps it means we are doing too much deco , how would we know ?
I have the same problem with helium deco. I have a written a well used trimix deco program, but I'm not that happy where the trimix deco theory comes from (just change the air coefficients from the air research)
My example of wind speed is about the discipline of scuba diving !. The equation is proportional to speed squared not speed.
We can judge the wind speed quite well buy holding your hand up to it (as from 10 to 14 knots you get an increase of force of a factor of 2 not 1.4)
I find deco a bit like engineering, it works well for the given situation. When we try to extend it futher we make approximations not backed up by evidence/theory (this comes from experience of design of electrical machines !). Mark elliots describes us "deco nerds" well in his book.
Tony
Nigel Hewitt
20-03-2007, 15:45
My example of wind speed is about the discipline of scuba diving !. The equation is proportional to speed squared not speed.
We can judge the wind speed quite well buy holding your hand up to it (as from 10 to 14 knots you get an increase of force of a factor of 2 not 1.4)OH I WISH!
My life has too much in the way of Reynolds numbers in it just to earn a crust.
Hi Janos. Let's do the quick one first. It could take me a while to type up the deep stops thing.
Anyhow. I mainly agree with you although I still think the best way to protect an OD from the dangers of rapid ascents is to encourage them to dive shallow and often. Whether the current OD qualification depth and limitations, as to whom and in what circumstance they can dive, helps to achieve that is another thread entirely ;)
Agreed. But it is not an either/or thing. We can teach people how to dive better AND give them the added protection of Nitrox.
Janos
I think you missed my point here.I think I understood it perfectly ;)
Most people except EAD because it makes sense (common sense ?) it is very simplistic maths. Just because it is simple does not mean it works
i.e. Newtonian mechanics is ok F=ma (simple) , but as things get faster they are not ok and are not longer a first order equations (thanks einstein).Conversly just because it is simple does not mean it does not work. The gas laws suggest EAD does work. There are applications other than scuba diving which do not entail the ethical problems of bending divers in order to provide proof. If there is an inadequacy in the simple laws we rely on I would expect experimentation and hypothesis in other disciplines to have identified the gap by now - as Einstein managed to do with Newtonian physics.
The knowledge of gas equations are old (I even studied at Uni for a laugh) but how that ppN" affects our body is not known still. If it was known we would have a model for deco (like a model for gas equations) rather than a the plethera we have.I am again inclined to turn the sentence around. If we knew more about how our bodies affect the gas laws we would have A model for deco rather than the plethora we do have! I am far from convinced that scuba decompression is such an extreme case as to 'break' the simple laws. Our bodies are a mass of liquid which a mass of gas can dissolve into. The unpredictable element is the interface between the liquid and gaseous states.
Pehaps END does require a slight change, perhaps it is an equation where absolute pressure is a variable as well ?I think it is more likely that the variable is physiology. The decompression problem is one of predictability. Gas and time can be controlled with a fair degree of accuracy. Pressure is variable in the sense that surface pressure changes but we can still measure it. The big unknown variable (the black box) is the body itself, it is highly complex and highly unpredictable. Improving those things we can already measure is unlikely to significantly improve the outcome of the prediction as the variance of individual physiology is so great as to overwhelm the improvement.
Perhaps it means we are doing too much deco , how would we know ?When you get out and don't get bent you have done too much deco!
The interesting thing for me is how the term 'bent' has been redefined in recent years. I well remember that in 1997 I was completing 90 minute air decompression having rushed up to 6m following the variable (20m/min to 6m/min) profile suggested by my shiny Aladin. Red Bull and Aspirin was the preferred apre dive refreshment but I never considered myself to have DCS. Over the years I have adopted a combination of good hydration, fixed 10m/min ascents, deep stops, higher FO2s. I can now complete more extreme dives, spend less time hanging and feel better getting out than when I got in. The EAD calculations I rely on do not completely explain the change in post dive symptoms. The deco times are equivalent in terms of Nitrogen content.
It seems 'common sense' to me now that the Aladin's suggested profile suited the gas laws, but did not suit me. The change in the ascent procedure apparently causes less physiological stress. There is plenty of anecdotal evidence and hypothesis to support my belief. But very little in the way of scientific proof.
I have the same problem with helium deco. I have a written a well used trimix deco program, but I'm not that happy where the trimix deco theory comes from (just change the air coefficients from the air research)Made all the more difficult by the different physical properties involved. At least we are used to breathing Oxygen and Nitrogen.
My example of wind speed is about the discipline of scuba diving !. The equation is proportional to speed squared not speed.
We can judge the wind speed quite well buy holding your hand up to it (as from 10 to 14 knots you get an increase of force of a factor of 2 not 1.4)That problem has been broken down, explained and expressed in math. The gas laws which describe how a mixture of gasses over a liquid are affected by pressure is also describable by math. The problem for scuba divers appears to be the processes which govern exactly how inert gasses traverse between the liquid state insode to the gasous state outside.
Unlike the models we use in deco predictions the body is not so neatly arranged and is highly dynamic. Even if we did know exactly how our bodies worked, we still have a multitude of variables to deal with. £billions have been invested in trying to predict the Weather. The terms of the equation are understood but the system they are applied to is so hugely variable that the predictions are still not correct. Decompression presents a similar problem. It is unlikely that we will ever be able to predict the difference between two people on two different days - well not in my lifetime anyhow.
I find deco a bit like engineering, it works well for the given situation.I find it more like cooking - eggs to be precise. The egg timer we use to cook an egg has virtually no relationship to the complex change in proteins which causes an egg white to harden while the yolk remains soft. The same can be said of decompression models, which have a very loose relationship to the physiological changes they attempt to predict. I don't think many people really appreciate just how rough a science deco modelling is.
When we try to extend it futher we make approximations not backed up by evidence/theory (this comes from experience of design of electrical machines !). Mark elliots describes us "deco nerds" well in his book.Have you met Mark Ellyat? Nice bloke but very much at the proving end, continuing to use models well past the parameters the authors regarded as sensible. Personally I regard 'deco nerds' as those people that are so focussed on the numeric details they forget to look at what it is they are trying to measure. They are busy watching the egg timer and ignoring what the egg tastes like.
OK am I missing something? Cos the SD nitrox workshop misses out on a couple of extremely important things:
1. equipment needed to dive nitrox. Doesn't mention O2 clean cyls, 40% max for normal kit etc.
2. How to analyse your nitrox. No point in diving it if you pick up a cyl that you reckon is 32% and it's pure O2. Or, as someone did recently, pick up a twinset, jump in the water, take 5 breaths then pass out as it was pure helium.
Or have I missed something?
Sean Gribben
23-03-2007, 12:59
Sports divers and above pre-2007DTP require to do both nitrox workshops if they were not nitrox certified.
NItrox workshop part 1 covers cleaning of cylinders and analysing of gas.
Sean
Ah. That would explain it.
In that case there is an error in the OD one- the BS for nitrox is BS 8478, not BS 7486. Which is a standard for video tape.
In that case there is an error in the OD one- the BS for nitrox is BS 8478, not BS 7486. Which is a standard for video tape.
Anyone else reminded of Red Dwarf and their Space Corps directives...
Janos
Anyone else reminded of Red Dwarf and their Space Corps directives...
Yes, and this thread is becoming a clear breach of Space Corps Directive 1742, if ever I've seen one...
Vic.
Adrian Kelland
23-03-2007, 14:16
Yes, and this thread is becoming a clear breach of Space Corps Directive 1742, if ever I've seen one...
Vic.
Right, who is wearing a ginger toupee then?
Right, who is wearing a ginger toupee then?
Well, I am wearing ginger, but that is by birth... :(
Mind if you ordered the nitrox standard from BSI for £78 or whatever and got one on video tapes you'd be a bit annoyed.
Smoke me a kipper. I'll be back for breakfast.
Yes, and this thread is becoming a clear breach of Space Corps Directive 1742, if ever I've seen one...
Vic.What, tapdancing in a box of mackerel while wearing a tutu and top hat is strictly forbidden? I don't see how that applies.
Steve in Sharm
23-03-2007, 16:11
What, tapdancing in a box of mackerel while wearing a tutu and top hat is strictly forbidden? I don't see how that applies.
Because the wearing of the top hat would push your ppM69 (mackeral) over 2.8 bar. Smeg head :rolleyes:
judithbodkin
23-03-2007, 16:43
One of the main reasons why I use nitrox I feel less tired after a dive. Also
feel a lot better generally. Plus if you have then got a long dive afterwards
I don't feel tired. Unlike diving on Air!!!!
Some other people that I know have switched to Nitrox because they were
getting headaches from diving on Air. Which they don't with using Nitrox.
:D :D :D :D
Adrian Kelland
23-03-2007, 16:48
What, tapdancing in a box of mackerel while wearing a tutu and top hat is strictly forbidden? I don't see how that applies.
Nope, that's Directive 1742(b)
One of the main reasons why I use nitrox I feel less tired after a dive. Also
feel a lot better generally. Plus if you have then got a long dive afterwards
I don't feel tired. Unlike diving on Air!!!!
Some other people that I know have switched to Nitrox because they were
getting headaches from diving on Air. Which they don't with using Nitrox.
:D :D :D :DApparently it's all a load of complete pants. The headaches are from rubbish oily air but the perceived benefits of nitrox are a placaebo effect. Page 2, claim #3.
More info here:
http://www.kitfondle.co.uk/images/nitrox/page1.gif
http://www.kitfondle.co.uk/images/nitrox/page2.gif
http://www.kitfondle.co.uk/images/nitrox/page3.gif
http://www.kitfondle.co.uk/images/nitrox/page4.gif
Apparently it's all a load of complete pants. The headaches are from rubbish oily air but the perceived benefits of nitrox are a placaebo effect. Page 2, claim #3.
More
I have never found any difference, however if one can take advantage of a placebo effect , do it !
I used to feel worse afetr a weekend on the coast teaching boat handing (always fell asleep in the car on the way home - as a passenger)
Tony
richard scarsbrook
24-03-2007, 01:00
In that case there is an error in the OD one- the BS for nitrox is BS 8478, not BS 7486. Which is a standard for video tape.
Well spotted. Actually it says BS 7478 which is the standard for the selection and use of thermostatic radiator valves. The leading 8 appears to have changed to a 7 somewhere in the drafting process. We'll correct it in due course. Hopefully nobody will confuse radiator valves for nitrox in the meantime :D
judithbodkin
24-03-2007, 08:22
Apparently it's all a load of complete pants. The headaches are from rubbish oily air but the perceived benefits of nitrox are a placaebo effect. Page 2, claim #3.
More info here:
http://www.kitfondle.co.uk/images/nitrox/page1.gif
http://www.kitfondle.co.uk/images/nitrox/page2.gif
http://www.kitfondle.co.uk/images/nitrox/page3.gif
http://www.kitfondle.co.uk/images/nitrox/page4.gif
Are you saying it's all of complete pants to the headaches? or all of what I
have said?
Diving on air and the jounrney found it differcult staying awake. Yet diving
on Nitrox wide awake. The other thing which I don't like with diving on air
the dryness in the mouth which I don't get with Nitrox.
Steve in Sharm
24-03-2007, 12:10
Are you saying it's all of complete pants to the headaches? or all of what I
have said?
Diving on air and the jounrney found it differcult staying awake. Yet diving
on Nitrox wide awake. The other thing which I don't like with diving on air
the dryness in the mouth which I don't get with Nitrox.
Woz is correct (and what is worrying is that as an instructor and local coaching scheme member, you should know this :rolleyes: ). The headaches are almost certainly down to poor fills rather than diving air instead of nitrox if there are no other extenuating circumstances - and it is well documented that the "feel better" effect is purely in your mind!! Read his links and it'll help you understand the "myths" better.
Steve
John Bantin
24-03-2007, 12:17
Because nitrox is double-filtered to prevent moisture getting into the tank's oxygen-rich interior it may be that it is cleaner than the poorly filtered (my suggestion) air that you have been used to. Headaches are almost certainly down to impurities given that your breathing technique and regulator is the same. Have you tried double-filtered Nitrox21?
judithbodkin
24-03-2007, 12:37
Woz is correct (and what is worrying is that as an instructor and local coaching scheme member, you should know this :rolleyes: ). The headaches are almost certainly down to poor fills rather than diving air instead of nitrox if there are no other extenuating circumstances - and it is well documented that the "feel better" effect is purely in your mind!! Read his links and it'll help you understand the "myths" better.
Steve
That was a bit below the belt.:(
Steve in Sharm
24-03-2007, 12:50
That was a bit below the belt.:(
Sorry if that's the way it came out, dont mean to be rude:o
But, the fact does remain that this sort stuff is "bread and butter" to an instructor, all instructors should know for instance that any gas that gets into your cylinder via a compressor has been filtered to remove any moisture from it and thats why we get a feeling of dry mouth - how many times have I had to explain that to a new student who thinks he's breathing "bad" air cos his/her mouth is dry....... and the lack of "dry mouth" when you dive Nitrox you mentioned is a figment of your imagination.
Another thing - do you want moist air corroding the inside of your cylinder!!! :eek:
Ditto the "well being" feelings etc etc etc.
Again, sorry - but your lack of undestanding of simple basics (as an instructor) does worry me, !!!!!.
Steve
judithbodkin
24-03-2007, 13:44
Sorry if that's the way it came out, dont mean to be rude:o
But, the fact does remain that this sort stuff is "bread and butter" to an instructor, all instructors should know for instance that any gas that gets into your cylinder via a compressor has been filtered to remove any moisture from it and thats why we get a feeling of dry mouth - how many times have I had to explain that to a new student who thinks he's breathing "bad" air cos his/her mouth is dry....... and the lack of "dry mouth" when you dive Nitrox you mentioned is a figment of your imagination.
Another thing - do you want moist air corroding the inside of your cylinder!!! :eek:
Ditto the "well being" feelings etc etc etc.
Again, sorry - but your lack of undestanding of simple basics (as an instructor) does worry me, !!!!!.
Steve
I'm not going to get into a argument with you. I do know the basics of Nitrox and I also the damage caused by moisture in a cylinder. I have also a done a
compressor course and I have also done a Gas Blending Course. Just because I haven't put all down in great detail it dose n't mean that I don't know
about basic Nitrox.:mad:
I have found your personal attack at me as being very rude and you have made this very public.:mad:
Steve in Sharm
24-03-2007, 15:40
I'm not going to get into a argument with you. I do know the basics of Nitrox and I also the damage caused by moisture in a cylinder. I have also a done a
compressor course and I have also done a Gas Blending Course. Just because I haven't put all down in great detail it dose n't mean that I don't know
about basic Nitrox.:mad:
I have found your personal attack at me as being very rude and you have made this very public.:mad:
Judith,
What part of
Sorry if that's the way it came out, dont mean to be rude :o
Didn't you understand? It was not a personal attack and was never meant to be! Sorry if you feel that way.
Steve
Richard Whitcombe
24-03-2007, 16:22
Id venture most diving headaches arent caused by the breathing gas at all. Its the breathing technique. Most headaches in diving are usually the result of CO2 retention.
judithbodkin
24-03-2007, 16:23
Judith,
What part of
Didn't you understand? It was not a personal attack and was never meant to be! Sorry if you feel that way.
Steve
It's when you make remarks like ("Again, sorry - but your lack of undestanding of simple basics (as an instructor) does worry me, !!!!!.")
Then you go to mention being on ("Coaching Team and it worries you etc").
There was no need for this. That is what I'm about talking about your personal
attack at me.
:mad:
Michael Purcell
24-03-2007, 17:50
In fairness Steve you can't just say:
Sorry if that's the way it came out, dont mean to be rude
and get away with whatever you want to say after that point.
Whether you meant it to be an attack or not, you were directly critical of her ability or even competency to BE an instructor. If you really felt it was a danger to people she trained a private discussion might have been a better avenue. (Even I went OUCH! when I read what you wrote the first time.)
*shrug*
What might be interesting to most BSAC divers is the latest theory on decompression- Mark Powell of Dive-Tech recently did a "Decompression and Physiology" lecture with us for a whole day and finding out about the ins and outs of deco beyond the (very) basics taught at BSAC level was great. Apparently there is a book to follow which shuld be on every diver's christmas list.
Anyway. Nitrox is good. Come up at 10 m/s to your ascent check depth. If you were running close to your no-deco limit on tables or computer then stick in a 3 min stop at 6 anyway. And dive nitrox on air tables. That's generally what I do in places like Scapa where you are doing multi-dive days with lots of 30m plus diving. Decompression theory is a load of guesswork anyway- you may as well make up your own rules and do it that way- it's about as valid.
Mike Halligan
26-03-2007, 13:52
Anyway. Nitrox is good. Come up at 10 m/s to your ascent check depth.
Eh? That's around 36kph, 25mph, knocking on.
Eh? That's around 36kph, 25mph, knocking on.Well I do fin quite fast.... :D
Ah yes, the 10 m/s ascent. No need to use the ladder/lift to get back on the boat then :)
I've never personally felt different after diving nitrox, but again that's probably because I've mostly used it to extend bottom times so the n2 loadings would be equivalent to my air dives. It does worry me that that different air is still being used in 'air only' dive cylinders, wouldn't it be simpler to have all diving gasses double/triple filtered?
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