Is my approach to diving with Nitrox logical?

[Nitrox_DiverNY]

Hello all I am looking for some feedback on my personal diving habits with Nitrox, and to see if my view point on it is incorrect?

Apart from extended NDLs I personally use Nitrox for its potential to reduce nitrogen loading thus contributing to DSC. I am certified up to the standard 40%, and I use as rich as a mix as I can regarding the MOD. For example I am doing dive with a max depth of 30-40ft, and had a cylinder filled as close to 40% as possible it came out to 39.8%. the mod of 40% at a pp02 of 1.4 is 82 ft. My point of view is get the mix as rich as possible as long as its not pushing the MOD at 1.4pp02, and spend the extra money for the extra safety margin, but this practice of using such rich fills seems few and far between. looking at the log book after my fill, it was mostly all 32% with one 36%. It seems like most people just go with the standard 32% even if (in my opinion) their mix cold be richer because they are nowhere near their mod.

The MOD of 40% at 1.4pp02 is around 82 ft, wouldn't using a 40% mix under that depth be a more conservative approach? so if your diving to a Max of 60 why not use 40%? I know DCS in rec is rare, but doesn't it make sense to use rich mixes when the dive allows to add in possible safety? why not be as safe as possible?


Does using a mix like 39-40% pose a substantially bigger risk to Low pressure oxygen toxicity (pulmonary oxygen toxicity), the the standard 32% even if the MOD is not pushed? If someone would be able to enlighten me more about this condition and how common it is with rich nitrox, that would be helpful.

when diving How close to 1.4pp02 will you allow yourself to get? I have never pushed it personally, but how close to 1.4pp02 do you find yourself on dives? do you go right up to it?

Is my logic on using rich mixes valid? Does anyone else share the same view point as me and also go as rich as possible? am I missing something? let me know in the comments, thanks !!

 

[tursiops]

Hello all I am looking for some feedback on my personal diving habits with Nitrox, and to see if my view point on it is incorrect?

Apart from extended NDLs I personally use Nitrox for its potential to reduce nitrogen loading thus contributing to DSC. I am certified up to the standard 40%, and I use as rich as a mix as I can regarding the MOD. For example I am doing dive with a max depth of 30-40ft, and had a cylinder filled as close to 40% as possible it came out to 39.8%. the mod of 40% at a pp02 of 1.4 is 82 ft. My point of view is get the mix as rich as possible as long as its not pushing the MOD at 1.4pp02, and spend the extra money for the extra safety margin, but this practice of using such rich fills seems few and far between. looking at the log book after my fill, it was mostly all 32% with one 36%. It seems like most people just go with the standard 32% even if (in my opinion) their mix cold be richer because they are nowhere near their mod.

The MOD of 40% at 1.4pp02 is around 82 ft, wouldn't using a 40% mix under that depth be a more conservative approach? so if your diving to a Max of 60 why not use 40%? I know DCS in rec is rare, but doesn't it make sense to use rich mixes when the dive allows to add in possible safety? why not be as safe as possible?


Does using a mix like 39-40% pose a substantially bigger risk to Low pressure oxygen toxicity (pulmonary oxygen toxicity), the the standard 32% even if the MOD is not pushed? If someone would be able to enlighten me more about this condition and how common it is with rich nitrox, that would be helpful.

when diving How close to 1.4pp02 will you allow yourself to get? I have never pushed it personally, but how close to 1.4pp02 do you find yourself on dives? do you go right up to it?

Is my logic on using rich mixes valid? Does anyone else share the same view point as me and also go as rich as possible? am I missing something? let me know in the comments, thanks !!

What you may be missing is that many nitrox providers are making the nitrox by pushing air through a semipermeable membrane that determines the O2 percentage by allowing oxygen through the membrane preferentially to nitrogen. Hold back more nitrogen, get a higher oxygen percentage in the output gas. Since 32% allows 100 ft dives with a safety factor, it gives nitrox advantages for most dives, without complications.

So, your quest for high-percentage nitrox mixes to limit your nitrogen uptake is not wrong, it is just increasingly hard to implement. A much easier way to limit nitrogen uptake is stay away from the NDL for your gas, no matter what the O2 percentage is.

 

[Johnoly]

am I missing something?

Most larger dive shops will store pre-mixed 32 or 36 ready to fill and use. That allows us to bring our tanks and wait for the fill. With gasoline prices at $4-$5, that extra trip to pickup a custom mix can be more expensive & time consuming than waiting while it's filled with a 'banked' fill. Add in your hourly wage when you could be doing something better like.......Reading ScubaBoard......and that premix total cost in time, gasoline, shop fill cost just went hugely negative versus the 3-5% O2 benefit. Now if it's Helium, by all means, LOL !!

 

[Searcaigh]

My standard mixes for my local diving, which are mainly square profile dives, are EAN34 and EAN40.

Our first dives are generally 27-30m and second dives 20-24m

Generally a one hour SI and very occasionally a third dive with a three hour SI after lunch, or a night dive using EAN34 if I bring my own gas or EAN32 if renting a tank from the dive op.

Most other divers outside our local group use EAN32 because that is the only mix to be offered. The disadvantage of using EAN32 for the second dive is the shorter NDL, which I don't mind as these divers surface sooner on the second dive leaving the dive site a bit more peaceful for me and my buddies to take photos.

 

[Marie13]

Can you get 36-40% without much hassle? Shops here usually charge a labor fee, plus the gas cost. Plus the 45 min drive each way at least. You have to drop tanks and come back another day. Not worth it. I’ll just take banked 32% which is readily available.

 

[Manatee Diver]

At 30-40ft the risk of DCS is so low that 40% is pointless. Mexico cave divers do 2-3 hour dives with average depths in that range using 32% and end with a surface gradient factor (how close they are to the deco required line) of under 10%.

 

[Jcp2]

Can you get 36-40% without much hassle? Shops here usually charge a labor fee, plus the gas cost. Plus the 45 min drive each way at least. You have to drop tanks and come back another day. Not worth it. I’ll just take banked 32% which is readily available.

I can and have gotten blends other than banked while I wait without a difference in charge ($15/tank) at a shop that happens to be a couple of miles from where I work.

 

[Marie13]

I can and have gotten blends other than banked while I wait without a difference in charge ($15/tank) at a shop that happens to be a couple of miles from where I work.

Lucky you. Waiting while they custom mix doesn’t exist here. Have to drop off and pick up in a day or two. Picking up the next day is not a sure thing.

 

[Nitrox_DiverNY]

What you may be missing is that many nitrox providers are making the nitrox by pushing air through a semipermeable membrane that determines the O2 percentage by allowing oxygen through the membrane preferentially to nitrogen. Hold back more nitrogen, get a higher oxygen percentage in the output gas. Since 32% allows 100 ft dives with a safety factor, it gives nitrox advantages for most dives, without complications.

So, your quest for high-percentage nitrox mixes to limit your nitrogen uptake is not wrong, it is just increasingly hard to implement. A much easier way to limit nitrogen uptake is stay away from the NDL for your gas, no matter what the O2 percentage is.

thanks, and very true about not pushing NDL

 

[Jcp2]

Hello all I am looking for some feedback on my personal diving habits with Nitrox, and to see if my view point on it is incorrect?

Apart from extended NDLs I personally use Nitrox for its potential to reduce nitrogen loading thus contributing to DSC. I am certified up to the standard 40%, and I use as rich as a mix as I can regarding the MOD. For example I am doing dive with a max depth of 30-40ft, and had a cylinder filled as close to 40% as possible it came out to 39.8%. the mod of 40% at a pp02 of 1.4 is 82 ft. My point of view is get the mix as rich as possible as long as its not pushing the MOD at 1.4pp02, and spend the extra money for the extra safety margin, but this practice of using such rich fills seems few and far between. looking at the log book after my fill, it was mostly all 32% with one 36%. It seems like most people just go with the standard 32% even if (in my opinion) their mix cold be richer because they are nowhere near their mod.

The MOD of 40% at 1.4pp02 is around 82 ft, wouldn't using a 40% mix under that depth be a more conservative approach? so if your diving to a Max of 60 why not use 40%? I know DCS in rec is rare, but doesn't it make sense to use rich mixes when the dive allows to add in possible safety? why not be as safe as possible?


Does using a mix like 39-40% pose a substantially bigger risk to Low pressure oxygen toxicity (pulmonary oxygen toxicity), the the standard 32% even if the MOD is not pushed? If someone would be able to enlighten me more about this condition and how common it is with rich nitrox, that would be helpful.

when diving How close to 1.4pp02 will you allow yourself to get? I have never pushed it personally, but how close to 1.4pp02 do you find yourself on dives? do you go right up to it?

Is my logic on using rich mixes valid? Does anyone else share the same view point as me and also go as rich as possible? am I missing something? let me know in the comments, thanks !!

If you go to the limit of NDL for the gas, then you are spending more time under for the same nitrogen load for a person using air going to the air NDL, and your surface intervals will be the same.