Using O2 on NDL dives

[WJefferis]

I have been thinking of taking an Advanced Nitrox/Deco Procedures class, but not for the most obvious reason of doing decompression dives (although I will do limited deco dives after completing the class). The biggest reason I would like to take it would be to also use 100% O2 on some of my recreationally deeper OW dives and to use after intro level dives (another class I will soon be taking). I wanted to use the 100% O2 during my safety stop for five minutes at 15 to 18 ffw/fsw.

The reason I want to do this is to add to my personal safety. I figure that if I am not pushing my NDL times and use 100% O2 on my safety stop of five minutes that I would really add to my safety by flushing out excess nitrogen from my system. I have heard of and know someone who has developed DCS even though others who were diving with them and had similar profiles were just fine. I just wanted to present this to tech/cave divers who regularly use 100% O2 and see what your opinions were on using O2 on NDL dives. Do you think it would add to safety or just be a total waste of money?

***please note that I only plan on doing this after being properly trained*****

[Mark Vlahos]

When cave diving I often breathe O2 at 20, then 15 feet. I like 2 or 3 minutes at 20 feet, and then 5 minutes at 15 feet. This is on dives where I stayed within the no deco limits. When I do incur a decompression obligation I like to stay at 15 feet on O2 for an additional 5 minutes. I don't do it on every dive, but I try to do it more often than not. Oxygen is relatively inexpensive. I also try to keep an eye on ascent rates during the dive, it is pretty easy to follow the contour of the cave and ascend too rapidly.

Mark Vlahos

[sandy]

I use an O2 bottle on many of my cave dives where I do not expect deco. Exceptions may be a dive in PI - Peanut or Twin Caves but that may change depending on dive plans for the day. I also use an O2 bottle for some deeper recreational wreck dives such as the Spiegel Grove.

Have fun with your class.

[Sludge]

I did a LOT of reading during the year Cave Diving: Articles and Opinions was being put together. Not just the articles that made it into the book, but many that didn't.

There is a theory that is coming around concerning the overuse of oxygen. I wish I could give citations, but I don't have them handy. Suffice it to say that some people feel that the body doing O2 at 1.6 is not a good thing over time.

I no longer even bring oxygen into the water unless I expect more than ten minutes of deco. I'm hoping someone with more knowledge will chime in here.

[RN]

Walter, I use O2 when it's required. If the dive I'm doing requires decompression, I will breathe O2. I will typically breathe it for the required amount of time plus an extra minute for every 5 minutes of required decompression at 20ft. I almost always add 3 minutes to every decompression less than 15 minutes. However, I don't breathe O2 if it's a no decompression dive. There's nothing wrong with doing it. It just hasn't seemed necessary to me. If you're doing a short dive in Twin, I don't see the point. If you're fighting the flow in JB, it might not be a bad idea. You have to evaluate each dive individually.

The incident you're referring to had a lot of other factors play into it. I was given the opportunity to review the profiles. One of the main things was a very liberal dive computer. Another was the saw tooth profiles caused by following the marine life.

[BobK]

I got bent doing an OW dive within NDL limits (barely within) that breathing O2 at 15 ft would probably have prevented. That being said, I still don't bother with O2 on NDL dives, I just spend more time at the 15 - 20 ft stop and hydrate better, which I think is more important. I don't think there is anything particularly bad about using O2 on NDL dives, and I know several people who do it regularly. Personally, I just don't think it makes much difference for properly conducted NDL dives.

[Line Squirrel]

IMHO being well hydrated would be better "insurance" for NDL dives as opposed to uinsg O2. I'm not knocking the use of O2 but I think there are an awful lot of divers that don't take a serious look at their pre dive fluid intake.

My first chamber ride was after a NDL recreationl dive. Looking at it after the fact I was probably pretty dehydrated and more than likely the primary cause of me taking a hit.

[Gary]

For an NDL dive breathing O2 on the surface would provide a better safety benefit without the risk of O2 tox and drowning. It is also warmer, drier and more convienient than carrying an O2 bottle into the water. O2 at <=1.0 ATA is considerably less toxic to the body than O2 at 1.6.

[Michael Stroeck]

For single NDL dives or very long surface intervals, I try to bring O2 along for emergency purposes, but don't take it into the water with me. I just ascend very slowly for the last 10 meters and have a good stop every single time.

For heavy repetitive diving, I like breathing it at around 1.3 ATA for a few minutes after every dive - I feel more fresh that way in the evening. I agree that hydration and physical fitness are probably more important, though.

[BigBoB]

50% makes more since for ndl dives in my opinion. Plus it provides for more of a bailout depth window if you have an OOA situation.