1.4 ....1.6...or ?????

[plclark196]

I recently did two dives with two dive buddies. Both dives were to 130 ft. I was diving air so I was not concerned with oxygen toxicity...however the other divers were diving eanx32. I mentioned to them at the start of the first dive that I thought they were pushing the depth limits for eanx32 as 110ft is the max depth at 1.4 ata and 130 is right at 1.6 ata.
They both expressed that those numbers are considered too conservative and that the Navy has indeed abandoned those numbers. Personally , I'm sticking to the 1.4. Any opinions???

 

[diverbob]

Most consider 1.4 better for the diving portion of the dive. 1.6 is usually recommended for doing deco, or "non-working" portion of a dive. Personally, I would not dive 32 to 130.

 

[battles2a5]

The standard use to be 1.6 and it was pulled back for a reason. You burn up the CNS clock very quickly at 1.6 compared to 1.4 and you are rolling the dice if diving at 1.6 for sustained time periods, especially if you are working hard. We still have no idea how to accurately predict an ox-tox episode, even within a specific individual. But we do know that the liklihood of toxing while in the working part of the dive is much higher at 1.6 than it is at 1.4. Using NDLs at that depth you aren't going to run your clock too high but that is a very bad attitude to take towards nitrox IMO.

 

[mkutyna]

There have been more at least a few instances where a diver has shown the symptoms of ox-tox at 1.3 ata during a long dive. Sure, some people are more susceptible to ox-tox than others. Would you really wanna test that out at 130' though?

 

[String]

BSAC allow 35m on 32% (1.44) for no stop dives only.

Really at these levels although there is a theoretical increased risk its tiny. Think of the shape of the risk curve.

If its a gentle dive, not much physical effort, first dive of a series and so on i wouldnt be overly concerned by that

 

[ScubaSteve]

BSAC allow 35m on 32% (1.44) for no stop dives only.

Really at these levels although there is a theoretical increased risk its tiny. Think of the shape of the risk curve.

If its a gentle dive, not much physical effort, first dive of a series and so on i wouldnt be overly concerned by that

The OP said nothing about how much exertion was required but BOTH dives were to 130' so not just the first of a series. Also, as you indicated, 32% is only good to 35m (or 114.8291 feet) which they exceeded on both dives.

The standard use to be 1.6 and it was pulled back for a reason. You burn up the CNS clock very quickly at 1.6 compared to 1.4 and you are rolling the dice if diving at 1.6 for sustained time periods, especially if you are working hard. We still have no idea how to accurately predict an ox-tox episode, even within a specific individual. But we do know that the liklihood of toxing while in the working part of the dive is much higher at 1.6 than it is at 1.4. Using NDLs at that depth you aren't going to run your clock too high but that is a very bad attitude to take towards nitrox IMO.

I whole heartedly agree. This is not somebody with whom there would be a third dive. I am not a maverick and do not want to dive with one. My life is worth more than that and I can stay within what I (ME) deem to be safe limits and hopefully live a long a fruitful life.

The maverick who cannot stay within what is deemed to be safe limits? Who knows. Once they push the limit once, they are more likely to continue pushing it farther each time.

 

[String]

The OP said nothing about how much exertion was required but BOTH dives were to 130' so not just the first of a series. Also, as you indicated, 32% is only good to 35m (or 114.8291 feet) which they exceeded on both dives.

Again maybe not a problem, we dont KNOW if it was hard work or not, we dont know the SI time and so on. It may or may not have been a problem, only the people with all the details can decide and at the end of the day its the individuals call. I cant say whether id do those dives myself or not without all the details.
This does highlight one of the major problems with Nitrox though - artificially limiting the MOD which if you dont know the site and so on in advance can create problems.
Its one of the reasons i dive air almost all the time as i can dive anywhere. Plus its 1/3 the price.

 

[ScubaSteve]

I do agree String. I have my Nitrox certification however dive air everywhere except places like Bonaire and liveaboards (assuming the staff deem it acceptable for the sites and conditions). Most of my diving does not warrant the expense (nor does it require the higher oxygen content) of Nitrox because they are usually simple, not deep dives. When I do dive Nitrox though, only I and my dive buddy know the conditions, depth etc. so only we know for sure whether we feel it was a good decision or not but barring something serious, I will always stay within my training and comfort. Deciding to push beyond that is going beyond your training in my opinion. Not my cup of tea personally.

 

[wedivebc]

There have been more at least a few instances where a diver has shown the symptoms of ox-tox at 1.3 ata during a long dive.

Are you sure about that? I have not heard of any verified cases below 1.4. If you have any references I would like to see them.

 

[String]

The only one i can think of from memory was a 1.3 "possible" hit "possibly" aggravated by pseudo-ephedrine and "possibly" CO2.

I dont recall a confirmed case.