02 on non deco dives

[Boomer7]

I am just finishing up my tech nitrox class, two more dives to do. The main reason I took the class was to increase the saftey factor of my diving. I have no intention of doing deco dives, right now. The class went over deco techneques and procedures. Here is where I still have questions. If I use o2 during my safty stops on non deco dives will that make a huge difference with the nitrogen in my system when I exit the water?
BR

 

[DepartureDiver]

Yes ... it will increase your safety upon surfacing and also increase your safety on repetitive dives. If you're going to do a safety stop (as you should), you might as make it as efficient as possible and use the O2.

 

[DandyDon]

robinsonboomer, are you talking about 100% O2, 40%, or what?

DepartureDiver, is there a recommended percentage and depth, or should I just wait for the class I'll be taking after the first of the year?

 

[DepartureDiver]

DepartureDiver, is there a recommended percentage and depth, or should I just wait for the class I'll be taking after the first of the year?

Wait for your class. I'm sure they will limit you to the gas percentage. Once you know how to do one mix, you can do any . . but the higher percentages give you less of a margin to make a mistake, i.e. if using 100% you must not accidentally go on it at 30' or accidentally dip below 20'. Also, the higher percentages require you to really make sure your regs are O2 clean and you didn't accidentally contaminate them. So playing with a lower percentage for awhile gives you time to play with everything. If you are staying in the recreational no-stop limits, my favorite mix for a single sling is 70% - which you can start at 40'. The 70% allows you to make some deep stops on your back gas, and then when you start make some slightly longer stops at the shallower depths, you get the benefit of a low nitrogen gas. But I'm sure you will start at 50% which you can switch to at 70' . . . which is a nice gas and depth. Since it can be used deeper, you can also use it as a bailout bottle if needed ... as long as you are shallow enough of course. Enjoy your class!

 

[MonkSeal]

If you are staying in the recreational no-stop limits, my favorite mix for a single sling is 70% - which you can start at 40'.

If you are staying in the recreational no-stop limits I see no point playing with high % O2 mixes, stage or deco tanks (except for training purposes). For "NDL" dives use EAN32 to 100' and do slow ascents with 2min stops at 20' and 10'.

 

[DepartureDiver]

The questions were intitally for Tech scenarios I believe, but I also believe divers benefit from nitrox other than EAN32 as well as a pony with a nitrox blend. During high nitrogen loads (as after a deep dive), gas washout is compromised upon surfacing. Also, gas management is an issue. Recreational divers often do not have the gas they need to bring themselves and their buddies back to the surface with a slow ascent and sufficient safety stops. An easy way to deal with an OOG situation is to carry a pony. This can be handled in two ways. One is to be able to breath from it at depth and the other is to share gas while ascending and then when a shallower depth is reached to switch at that time. So if a pony is going to be carried, why not have it enriched with nitrox so nice offgassing occurs during the safety stops. Also, I believe the stops need to start deeper than 20' when performing deep dives.

 

[Boomer7]

The questions were intitally for Tech scenarios I believe, but I also believe divers benefit from nitrox other than EAN32 as well as a pony with a nitrox blend. During high nitrogen loads (as after a deep dive), gas washout is compromised upon surfacing. Also, gas management is an issue. Recreational divers often do not have the gas they need to bring themselves and their buddies back to the surface with a slow ascent and sufficient safety stops. An easy way to deal with an OOG situation is to carry a pony. This can be handled in two ways. One is to be able to breath from it at depth and the other is to share gas while ascending and then when a shallower depth is reached to switch at that time. So if a pony is going to be carried, why not have it enriched with nitrox so nice offgassing occurs during the safety stops. Also, I believe the stops need to start deeper than 20' when performing deep dives.

I am also a believer in the deep stops. It is not only safer but I feel alot better at the end of the day. I was originally tthinking of using 100%O2 but after reading some of the comments I may go for a 75% mix, just to increase my margan of error.
BR

 

[MonkSeal]

The questions were intitally for Tech scenarios I believe, but I also believe divers benefit from nitrox other than EAN32 as well as a pony with a nitrox blend. During high nitrogen loads (as after a deep dive), gas washout is compromised upon surfacing. Also, gas management is an issue. Recreational divers often do not have the gas they need to bring themselves and their buddies back to the surface with a slow ascent and sufficient safety stops. An easy way to deal with an OOG situation is to carry a pony. This can be handled in two ways. One is to be able to breath from it at depth and the other is to share gas while ascending and then when a shallower depth is reached to switch at that time. So if a pony is going to be carried, why not have it enriched with nitrox so nice offgassing occurs during the safety stops. Also, I believe the stops need to start deeper than 20' when performing deep dives.

First, yes I agree that deep stops should be started deeper than 20' (e.g. at 70% depth or 80% ATA and then 1 min for each 10' or something according some bubble concerning algorithm like RGBM or whatever works for you).

But I can't agree on carrying pony with any high O2 (meaning above 40%) in recreational diving. Carrying such tank requires skills that are beyond average recreational diving. The cause of the original problem you're reffering (OOG) is poor gas management skills or lack of decompression tehniques knowledge which can't be solved by carrying a pony.

 

[DA Aquamaster]

My preference is to use 50%. In a moderate deco situation you only add a few minutes compared to 80% and are normally about the same in terms of run time compared to 100%. But with 50% you can switch for your deep stop and ascent at 70ft and this makes it is very compatible with the current 1/2 the max depth saftey stop concept beginning to be used by many recreational divers as well as with gradient factor and variable permiability decompression models used by many technical divers.

I am not sure that the degree of difference between 50% and the 40% you end up certified to use in a nitrox course is really all that significant, but an advanced nitrox course is a good idea as is a deco procedures course.

One operational benefit of 50% is that you can efficiently blend it with simpler equipment by transfilling as you only need 1101 psi of O2 to fill a 3000 psi tank. 70% is about the max you can get by transfilling and then only with a fairly full tank of O2. 80% is firmly in boost pump territory.

A pony/deco/sling bottle (whatever you want to call it) filled with 50% can also obviously be used as a bailout for depths of 70 ft or less and you can always potentially do what amounts to an ESA from deeper depths to 70'.

 

[DepartureDiver]

I agree training for high O2 mixes is needed otherwise it is a disaster waiting to happen and didn't mean to imply otherwise. My suggestion was for those that received the training or are about to take the class such as DandyDon and BR and of course should only be used by those that are comfortable ascending and monitoring depth before a gas switch, including in any stressful situation ... so thanks for helping this to be clarified.