CALI68
Contributor
I am about to start diving with Nitrox and I had some questions. I asked Boogie711, a known Guru on the board and here is the PM discussion we had. This is very useful information from a highly knowledgeable person.
FROM CALI68: Hi! I'm sorry to bother you but you always give well thought out, intelligent responses so I figured you would be a good guy to ask a couple questions to.
I am brand new, newbie as can be to Nitrox. I know very little about it but what I do know makes me want to learn, understand and apply it. The questions I have are:
1) My Reg. is "factory ready" for Nitrox although I have been using it with air for a year. Is there a special cleaning process it must go through and if so how much do those run?
2) My tanks are Pressed Steel E7 80's and the same thing applies for those. I have been using them for about 6 months with air.
3) What's the range of diving (in terms of depth) that Nitrox would be most useful? I heard it's very dangerous for diving deeper than 100'
Finally, Should I take a PADI Enriched air course or is there another course you would recommend?
Thank You for your time.
-Chris
FROM BOOGIE711: Hey Chris... ok, let's try to knock this off in order. Generally, as long as anything is under 40% O2, you should be OK without having it O2 cleaned. Which means:
a) don't worry about the regs. By the time anything gets to your regulator, you'll be breathing less than 40% anyway.
b) If your LDS pre-mixes Nitrox, your tanks will be fine. However, it's worth getting them O2 cleaned because many (most, in my experience) partial pressure blend - they add pure O2 first, then top off with air to get the desired O2 percentage. Since there's 100% O2 flowing into a tank, you're going to want to strip any of the hydrocarbons that come with normal 'air' out of their. O2 cleaning costs vary from LDS, but figure about $40 per tank or so, give or take $10-$15.
c) The caveat on this is if the ONLY place you've been getting regular "air" fills already pumps Nitrox. If that's the case, chances are good that the air that goes in there is already hyperfiltered clean, and free of most hydrocarbons. Then again, you should get tanks O2 cleaned every year anyway, so it's not a bad idea.
Nitrox is great for depths of between 60 and 110 feet or so. Oxygen is toxic at depth, and the partial pressure of O2 increases with depth. For example, on the surface, the "partial pressure of Oxygen" (ppO2) is .21 (since we're right now breathing 21% O2.) At 33 feet, it would be .42, at 66 feet it would be .63, etc.
You want to keep your O2 percentage below 1.4. That means that for your most common blend (I'm DIR and I ONLY dive recreational depths with 32%) you're limited to 111 feet. If you're diving 36%, which is another common blend, you're limited to 94 feet - since the higher O2% means the ppO2 1.4 limit is reached sooner. Does that make sense? Where Nitrox is great is on a typical 100 foot dive - where your NDL limit is normally 10 minutes, on 32% it's over twice as long.
You definitely want to take a Nitrox course. In fact, you won't be able to get Nitrox fills in a lot of places without a Nitrox certification. I don't really like PADI as an organization, but blah blah blah -it's the instructor, not the agency. I have some really good DIR dive buddies who were originally trained PADI. But be sure you get an instructor who doesn't mind if you ask a lot of questions. The Nitrox class is mostly classroom stuff, going over O2 limits and symptoms of oxygen toxicity, stuff like that.
Hope that helps. It's not difficult stuff to learn, but it's worth doing. What I just threw at you isn't even Nitrox 101 - more like Nitrox 50.5, but if you have any questions, let me know.
CALI68: I can't thank you enough for your time! That all really makes sense.
One last question:
On dives with a more average depth like say 60' is it good or bad or does it matter if you use Nitrox? Do you get a longer bottom time?
BOOGIE711: The DIR answer is - I dive 32% all the time. Covers me for everything from 2 feet to 110 feet. Is there a discernable benefit on shallower dives? Probably not a whole lot, but it's definitely not going to hurt. It also makes dive planning really simple. The other week, I did a 30 minute dive at 60 feet. SI of about an hour, then wanted to go back in and do the same wreck. I just jumped in - even on air, you get 60 minutes at 60 feet, so on Nitrox, I knew I wouldn't even be CLOSE to NDL's. Even if it doesn't affect NDL times, less nitrogen is always a good thing, right?
FROM CALI68: Hi! I'm sorry to bother you but you always give well thought out, intelligent responses so I figured you would be a good guy to ask a couple questions to.
I am brand new, newbie as can be to Nitrox. I know very little about it but what I do know makes me want to learn, understand and apply it. The questions I have are:
1) My Reg. is "factory ready" for Nitrox although I have been using it with air for a year. Is there a special cleaning process it must go through and if so how much do those run?
2) My tanks are Pressed Steel E7 80's and the same thing applies for those. I have been using them for about 6 months with air.
3) What's the range of diving (in terms of depth) that Nitrox would be most useful? I heard it's very dangerous for diving deeper than 100'
Finally, Should I take a PADI Enriched air course or is there another course you would recommend?
Thank You for your time.
-Chris
FROM BOOGIE711: Hey Chris... ok, let's try to knock this off in order. Generally, as long as anything is under 40% O2, you should be OK without having it O2 cleaned. Which means:
a) don't worry about the regs. By the time anything gets to your regulator, you'll be breathing less than 40% anyway.
b) If your LDS pre-mixes Nitrox, your tanks will be fine. However, it's worth getting them O2 cleaned because many (most, in my experience) partial pressure blend - they add pure O2 first, then top off with air to get the desired O2 percentage. Since there's 100% O2 flowing into a tank, you're going to want to strip any of the hydrocarbons that come with normal 'air' out of their. O2 cleaning costs vary from LDS, but figure about $40 per tank or so, give or take $10-$15.
c) The caveat on this is if the ONLY place you've been getting regular "air" fills already pumps Nitrox. If that's the case, chances are good that the air that goes in there is already hyperfiltered clean, and free of most hydrocarbons. Then again, you should get tanks O2 cleaned every year anyway, so it's not a bad idea.
Nitrox is great for depths of between 60 and 110 feet or so. Oxygen is toxic at depth, and the partial pressure of O2 increases with depth. For example, on the surface, the "partial pressure of Oxygen" (ppO2) is .21 (since we're right now breathing 21% O2.) At 33 feet, it would be .42, at 66 feet it would be .63, etc.
You want to keep your O2 percentage below 1.4. That means that for your most common blend (I'm DIR and I ONLY dive recreational depths with 32%) you're limited to 111 feet. If you're diving 36%, which is another common blend, you're limited to 94 feet - since the higher O2% means the ppO2 1.4 limit is reached sooner. Does that make sense? Where Nitrox is great is on a typical 100 foot dive - where your NDL limit is normally 10 minutes, on 32% it's over twice as long.
You definitely want to take a Nitrox course. In fact, you won't be able to get Nitrox fills in a lot of places without a Nitrox certification. I don't really like PADI as an organization, but blah blah blah -it's the instructor, not the agency. I have some really good DIR dive buddies who were originally trained PADI. But be sure you get an instructor who doesn't mind if you ask a lot of questions. The Nitrox class is mostly classroom stuff, going over O2 limits and symptoms of oxygen toxicity, stuff like that.
Hope that helps. It's not difficult stuff to learn, but it's worth doing. What I just threw at you isn't even Nitrox 101 - more like Nitrox 50.5, but if you have any questions, let me know.
CALI68: I can't thank you enough for your time! That all really makes sense.
One last question:
On dives with a more average depth like say 60' is it good or bad or does it matter if you use Nitrox? Do you get a longer bottom time?
BOOGIE711: The DIR answer is - I dive 32% all the time. Covers me for everything from 2 feet to 110 feet. Is there a discernable benefit on shallower dives? Probably not a whole lot, but it's definitely not going to hurt. It also makes dive planning really simple. The other week, I did a 30 minute dive at 60 feet. SI of about an hour, then wanted to go back in and do the same wreck. I just jumped in - even on air, you get 60 minutes at 60 feet, so on Nitrox, I knew I wouldn't even be CLOSE to NDL's. Even if it doesn't affect NDL times, less nitrogen is always a good thing, right?
