I am 58 and dive twice a year . 10 dives per trip. i'm in fair shape. i'm looking onto doing a nitrox course. I'm not sure this will be a positive or not. i will heve less nitrogen building up , but now i'll have to moniter O2. I'm puzzeled as weather this is for me. Any advise?
Nitrox pros and con
- Thread starter cwaver
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teknitroxdiver
Contributor
On an average dive, do you run out of air or time first?
If you run out of air, you won't see much benefit from nitrox, except shortened surface intervals.
If you're running out of bottom time with air left, then nitrox will be a big plus for your dives.
If you run out of air, you won't see much benefit from nitrox, except shortened surface intervals.
If you're running out of bottom time with air left, then nitrox will be a big plus for your dives.
Daryl Morse
Contributor
Even if you don't run out of NDL, if you dive nitrox on an air profile, it provides an additional safety margin, which cannot hurt.teknitroxdiver:
The only "downsides" are that you have to consider PO2 and it costs more, neither of which are big deals.
As indicated above, if you are running out of no deco time on air well before you run out of air, Nitrox may be a big advantage in terms of extending bottom time.
However, Nitrox also gives you the option of diving Nitrox while using air tables or an air computer to provide an added degree of safety. This can be a big plus for older divers who may be getting farther and farther away from the parameters considered normal in most deco models. This can be particularly valuable on dive trips where you are doing repetitive dives over multiple days - a profile that pushes or exceed the prudent limits of most computers and tables regardless of age.
With regard to O2 exposure, there are 2 things to consider, your PPO2 and your total exposure (CNS clock). But in practice there is really not much to watch as you really have to push it and spend a fair amount of time in the water to approach the limits. And by then you will have long since had to start doing deco due to nitrogen loading.
From a practical standpoint, recreational divers doing no deco dives will find that nitrogen loading always imposes a limit long before the CNS clock is exceeded.
For example, if you plan to stay at or below a PO2 of 1.4 at depth, you can accummulate 150 minutes on a single dive and 180 minutes in a 24 hour period. (And this is actually pretty conservative as it is based on NOAA standards that do not give you credit for surface intervals.) So on 32% nitrox you could dive to 110 ft before you exceed a 1.4 PPO2 and stay for 25 minutes before you exceed the NDL. With 36% Nitrox, you could go to 95 ft and not exceed 1.4 and stay there for 40 minutes with no deco obligation. Consequently, in the worst case scenario you would have to do 4 dives to 95 ft for 40 minutes each on 36% nitrox in a 24 hour period before you would have to start worrying about the CNS clock. From a deco standpoint that is not possible as you will find you need deco stops to do the repetetive dives within the 24 hour period.
With a higher (and less conservative) PPO2 of 1.6 the limits get a little tighter, but not much as you are still allowed a maximum of 45 minutes for a single dive and 150 minutes total in 24 hours. So you can do a 130 ft dive on 32% for 15 minutes or you can use 36% to make a 106 ft dive for 30 minutes. But again you will exceed the no deco limits if you try to actually do five 30 minute dives to 110 ft within 24 hours.
So in practice, all you need to watch is the maximum operating depth for a given nitrox mix and the rest of the theory covered in the class on the CNS clock is just that - theoretical.
However, Nitrox also gives you the option of diving Nitrox while using air tables or an air computer to provide an added degree of safety. This can be a big plus for older divers who may be getting farther and farther away from the parameters considered normal in most deco models. This can be particularly valuable on dive trips where you are doing repetitive dives over multiple days - a profile that pushes or exceed the prudent limits of most computers and tables regardless of age.
With regard to O2 exposure, there are 2 things to consider, your PPO2 and your total exposure (CNS clock). But in practice there is really not much to watch as you really have to push it and spend a fair amount of time in the water to approach the limits. And by then you will have long since had to start doing deco due to nitrogen loading.
From a practical standpoint, recreational divers doing no deco dives will find that nitrogen loading always imposes a limit long before the CNS clock is exceeded.
For example, if you plan to stay at or below a PO2 of 1.4 at depth, you can accummulate 150 minutes on a single dive and 180 minutes in a 24 hour period. (And this is actually pretty conservative as it is based on NOAA standards that do not give you credit for surface intervals.) So on 32% nitrox you could dive to 110 ft before you exceed a 1.4 PPO2 and stay for 25 minutes before you exceed the NDL. With 36% Nitrox, you could go to 95 ft and not exceed 1.4 and stay there for 40 minutes with no deco obligation. Consequently, in the worst case scenario you would have to do 4 dives to 95 ft for 40 minutes each on 36% nitrox in a 24 hour period before you would have to start worrying about the CNS clock. From a deco standpoint that is not possible as you will find you need deco stops to do the repetetive dives within the 24 hour period.
With a higher (and less conservative) PPO2 of 1.6 the limits get a little tighter, but not much as you are still allowed a maximum of 45 minutes for a single dive and 150 minutes total in 24 hours. So you can do a 130 ft dive on 32% for 15 minutes or you can use 36% to make a 106 ft dive for 30 minutes. But again you will exceed the no deco limits if you try to actually do five 30 minute dives to 110 ft within 24 hours.
So in practice, all you need to watch is the maximum operating depth for a given nitrox mix and the rest of the theory covered in the class on the CNS clock is just that - theoretical.
jakubson
Contributor
Assuming your "10 dives per trip" are 5 days of two dives per day, your only worry about PO2 involves maximum depth. At a "normal" resort mixture of 32%, your maximum depth is 111 ft. As an occasional diver at your age, I don't think this is a big limitation. You can either dive a Nitrox profile for longer dives (or shorter surface intervals as teknotroxdiver pointed out), or you can dive air profiles for more safety margin (as Daryl pointed out.)Daryl Morse:
PS - DA Aquamaster posted while i was typing mine - he said similar things with much more detail.
I guess you could say that I've dived a lot of nitrox and I haven't found a down side to it.
Resort divers especially those who don't dive often and/or are not teenagers any more are probably amoung those who benefit the most. Bunches of dives per day, possibly less that graceful ascents, vacation night life after diving, the irregular diet and hydration that travel sometimes includes and a flight home all set you up just about right to get one of those undeserved hits we hear about so often.
Resort divers especially those who don't dive often and/or are not teenagers any more are probably amoung those who benefit the most. Bunches of dives per day, possibly less that graceful ascents, vacation night life after diving, the irregular diet and hydration that travel sometimes includes and a flight home all set you up just about right to get one of those undeserved hits we hear about so often.
Kriterian
Guest
cwaver:
I don't think there is any disadvantage to taking the course, other than the cost, and getting more information on Nitrox. I didn't see it mentioned but nitrox seems to help reduce fatigue after the dive is over. Most of the "senior" members of my local dive shop playfully refer to Nitrox as "Geezer Gas" and won't dive anything else.
A little more information on your dive trips may help us give you better advice too. Nitrox would definitely be beneficial to you if your trips are two days with five dives per day instead of five days with two dives per day.
I can't actually think of a down side. You're old enough to know the value of prevention, so that's one in your favor. If you like to tinker and pay attention to your diving, nitrox is a fun addition to add to the mix. Less nitrogen in your tissues - less taxing on your (not 21 year old) body. So far all I see are positives... I've always thought that nitrox is a no-brainer for the grownups.
A downside may be that if you own your own tanks, where you get fills (nitrox or air) may be more limited. If you keep your tanks O2 clean, you cannot fill with air that is not O2 compatible. Not all fill stations will be able to provide O2 compatible air. But based on your description of the diving you do, I'm guessing you don't own your own tanks.
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