DCS in Cozumel
- Thread starter Butch Fries
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Correct. My lack of precision.
The unspoken implied part was "an incidence of 25% if having a PFO didn't make any difference." Thank you for clarifying.
The unspoken implied part was "an incidence of 25% if having a PFO didn't make any difference." Thank you for clarifying.
Just for clarity that is true if you dive BOTH air and Nitrox to the NDL limits. However, I dive it to extend bottom time as I used to smash an 80 right up the the NDL with air left. Now I dive nitrox and the tank is the limiting factor, hence I extend bottom time and have less loading than I did on air. Just pointing out you can be safer and have longer BT if you are in the middle like me.
Ummm - maybe we're talking about 2 different things - but if you are extending bottom time following nitrox tables - then you are still loading more N2 - i other words, if you are doing a profile where the NDL for air is 25 minutes but you are diving it on 36% and you extend your bottom time accordingly, you are still maxing out your NDL so no extra margin of safety. Using a computer on a multi-level dive, I dive with two computers. One is set to air which is what I actually follow for bottom time - the other is set to the nitrox mix I am using so that I know how much O2 I am loading. Not sure if I'm being clear?
It's surprising how many people believe that diving Nitrox will extend their bottom time by somehow stretching out their air consumption (not saying this is you Chief) - just to be clear to those folks out there who think that is the reason for nitrox - Nitrox does not change your air consumption. If you go through an AL 80 on air in 40 minutes, you will go through a tank of nitrox in 40 minutes
Maybe you are missing me?
Example 1 on air my NDL is say 60 minutes. At 60 minutes I have air left and surface. I now have the maximum amount of nitrogen in my system that my computer allows.
Example 2 on nitrox my NDL is now 120 minutes. However at 90 minutes I am out of gas and I surface. I have well LESS nitrogen in my system than my computer would allow. Had I the gas, I could have stayed another 30 minutes before reaching the same nitrogen loading as example 1.
So in example 2 I extended my bottom time AND have less nitrogen loading than example 1. That is the middle ground I am talking about. Some extending bottom time and some reduced nitrogen loading. I think that is kind of important to note that you can both extend bottom time AND load less nitrogen with nitrox.
And it tend to be truthful for me. Trying to keep up with Susanita, I am now limited by quantity of gas not NDL. I used to run 100CF of air to keep up with her on a 80 of nitrox, but eventually I was constantly limited by NDL. Now diving nitrox, I am limited by gas quantity and not NDL for the most part.
I am sure for those that can run an 80 of air up to NDL, not all of them can run a tank of nitrox to NDL before running out of gas.
I think people should consider nitrox to both reduce nitrogen loading and extend bottom time.
Oh and I dive a Mares, so I am ALREADY diving conservative.
Brodydog
Contributor
That's what we do, especially for multiples dives in a day and/or deeper dives (not exceeding nitrox depth limits). It isn't for the benefit of feeling better on nitrox, I can't tell a difference with air or nitrox after the dive.
I got nitrox certified on a Tucks and Caicos liveaboard. I was running out of bottom time too quickly with each consecutive dive in the same day. Nitrox keeps me down longer for sure.
Because I dive nitrox strictly on air limits - the tracking of the O2 is just in case, although I'm never doing more than 2 dives a day anymore so it really isn't totally necessary. The computer set to actual O2 setting also serves as a back-up. My computer has various settings in re conservatism - and mine are both set to the most conservative profiles already.
I know it's not practical for everyone, but I always recommend having a back-up computer. I can't tell you how many people's computers crap out on them in the middle of a dive week - either battery, flooding or some other problem then they want to rent a computer. Sorry to say folks, but we can't rent you a computer once you've started diving, unless you take a full 24 hours off first - it has no idea what your previous profiles were.
That is a really good idea I think!
We dive Mares wrist computers, but I stuck scubapros in the console as a backup. Of course then EVERY time I used them the scubapros went dead. Sent them to Javi to get the battery replaced. After several cycles of that, now the batteries seem to work. In the meantime, I forgot the complicated scubapro interface. So the dang things are set on 36 all the time....
So, maybe in addition to the second computer I should learn to use the darn thing again....
Thanks Christi. I decided to go with a conservative algorithm rather then air on nitrox settings. I too dive 2 computers and follow the most conservative for any given dive. So far so good. Most recently I have started watching my GF on ascent and trying to keep it low.
I have never rashed in Bonaire even though I do 3 to 4 dives a day (very rarely 5) for a week. But the dives all have very shallow average depths with the final half of the dive usually spent at 30 to 20 feet.
I rashed once in Cozumel. It was my first trip to the island. It happened the second day of diving with just two dives a day but long dives. And it was an op that insisted on all ascending together so I didn’t have the control over my dives that I need to stay safe.
Since then I found a dive op that trusts me to manage my own dives and have not rashed despite 2 to 4 dives a day (Hope I didn’t just jinx myself) including Devil’s Throat the last trip. I have found that, for me, its not the absolute depth or time under water but a combination of the entire dive including safety stops.
I have never rashed in Bonaire even though I do 3 to 4 dives a day (very rarely 5) for a week. But the dives all have very shallow average depths with the final half of the dive usually spent at 30 to 20 feet.
I rashed once in Cozumel. It was my first trip to the island. It happened the second day of diving with just two dives a day but long dives. And it was an op that insisted on all ascending together so I didn’t have the control over my dives that I need to stay safe.
Since then I found a dive op that trusts me to manage my own dives and have not rashed despite 2 to 4 dives a day (Hope I didn’t just jinx myself) including Devil’s Throat the last trip. I have found that, for me, its not the absolute depth or time under water but a combination of the entire dive including safety stops.
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