Deepest safe depth on air?

[Gary D.]

true.....but at depths close to 200' on air I am sure most people will get or have been narced

Again it depends on the person and conditions. There isn't a depth where a person will be narced everytime.

I have been fine on a chamber ride over 250 and so narced just over 150 I was looking for a cocktail waitress. Different days have different results.

Gary D.

 

[Al Mialkovsky]

Define "safe".

In terms of Oxygen Toxicity the PPO2 of 1.6 using air is 66m (213ft). You really dont want to be here.

PPO2 of 1.4 for air is 56m (183ft).


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It's the toxicity that gets you more than narcosis. Convulsions are never pleasant. I've been to 215 on air and the narcosis was nearly overwhelming but my fear was oxygen toxicity.

 

[String]

It's the toxicity that gets you more than narcosis. Convulsions are never pleasant. I've been to 215 on air and the narcosis was nearly overwhelming but my fear was oxygen toxicity.

Depends entirely on the diver.

Myself and others i know of would be so narc'd at depths well above that it isnt safe by any measure. Overwhealming narcosis can make you do very silly things and if anything goes wrong can stop you acting properly or quickly to fix it. Thats the main reason for my self imposed limit on air as opposed to O2 tox. Conculsions definately arent pleasant but on the other hand neither is removing your kit, trying to breathe without your reg or panicing and bolting from depth due to narcosis.

I can simulate the O2 tox fear by diving a nitrox mix shallower so i guess im used to being a bit cautious over that. Its something i can deal with. Narcosis is something i dont trust.

 

[DA Aquamaster]

It's a basic scuba forum, so I'll add the disclaimer that for a recreational diver, the max depth is 130 ft. Period. And then only if they have AOW certification and a deep specialty.

When you start talking depths below 130', you are talking about having to take a at least one and more likely two technical diving courses, at least if you want to be certified to do go below 130 ft.

TDI used to certify perople to 170' with the combination of Deco Procedures and Advanced Nitrox but has sinced backed that off to 150'. They still certify people to 180' on air with their Extended Range course.

PSA does offer a certification to 240 on air...but they are pretty conservative about giving it out. For many divers they will eventually take them to 240 ft if they work down through all the levels, but they may not neccesarily give them the certification. In practice, they hold people at the 150 ft level until they see what they need to see in terms of ability to perform adequately before stepping deeper.

Personally, I am comfortable at 150' if I step down gradually over a period of a couple weeks at the start of the season and continue to dive deep on a regular basis over the course of the season. I am however also very careful to set very conservastive and finite limits for the conditions of the dive and plan to keep the dive well within the limits of my past ability and experience.

ALso, in my experience CO2 levels affect my suscpetibility to narcosis. So I use a very easy breathing regulator and I plan the dive to keep exertion at a minimum.

In my opinion, to dive deep safely on air requires that your diving skills be second nature and your reponses to emergencies be so well ingrained as to be automatic. Nitorgen narcosis effects everyone below 130 ft so you need to be sure the demands of the dive will not exceed the limits of your impaired cognitive skills and physical coordination in an emergency. People differ in their skill level, their ability to function under a given degree of nitrogen narcosis, and in there susceptibility to narcosis. So the "safe" depth limits of individual divers will vary from diver to diver and from day to day.

 

[String]

It's a basic scuba forum, so I'll add the disclaimer that for a recreational diver, the max depth is 130 ft. Period.

Only for some agencies......

 

[D1V3R]

It just depends on the conditions, back in the 70's my dad would do long cave dives down to 240' on air

 

[Diver Dennis]

It depends where you are diving as well. In Truk Lagoon for example, there are quite a few deep dives, especially the San Francisco, that is about 170' to the deck. Most divers that go there do this dive.

 

[String]

It depends where you are diving as well. In Truk Lagoon for example, there are quite a few deep dives, especially the San Francisco, that is about 170' to the deck. Most divers that go there do this dive.

Again thats down to the divers acceptable of risk and what they're willing to accept.

Truk is warm, clear water so generally not as "bad" as a cold deep dark high current narc.

Plus trimix isnt available so you want to do the divers there, air is the only real option.

 

[Nemrod]

I have been over 150 quite a few times, over 200 several times, and 235ish once. All of those dives were well palnned, not a lark, and there was something there I wanted to see or do. Narcosis is unpredictable and some people are more prone to it's effects than others but no one is immune. From a practical standpoint, 130 feet is the limit--for me---only exceeding that under special conditions or need. Narcosis is a serious threat and some people can begin seeing the effect before 100 feet. Things such as being fatigued, drinking, fitness, medications, who knows could effect the suseptability. N

 

[cummings66]

It's the toxicity that gets you more than narcosis. Convulsions are never pleasant. I've been to 215 on air and the narcosis was nearly overwhelming but my fear was oxygen toxicity.

I've got to say based on my experiences that my limit is 100'. I was down to 119 feet and I was seriously narc'd. I knew it at the time and had basic control but I was not thinking right which I knew once I got out of the water and debriefed my dive.

Short scarry story follows and my lesson learned. To steal something from AOPA's mag, "Never again"

I last remember looking at my depth at 94 feet, next I looked I knew I was deeper than 100 but I was not sure how deep because I couldn't make sense of the display. All I could read on it was the number one and the rest looked chinese to me, that was it. I could decipher my analog SPG easily and when I hit my turn point I signaled to go up but I had lost track of time at depth because I couldn't read. In fact I was very close to exceeding my NDL limits. My SAC is good enough that I can exceed NDL limits while using Rock Bottom times, thankfully it's not that much better. I was well aware of the air supply because I've had to donate air before and I found out how quickly the other diver can use it up, so I've started using Rock Bottom times and that means I come up with more air in my tanks at the start than many do. For me, air is one of the most important thing to worry about and I know that even when my brain starts shutting down I still think about my air levels.

During that time at depth I had weird things going on that later on scared me after I thought about it. My buddy was at 122 feet and I wanted so bad to be next to him at the computer desk there that I thought I dumped my BC, drysuit, and also exhaled all my air, plus I tried to swim down to him but for some reason I never got any closer. I really thought I did all that but I hadn't done any of it, in fact the great pics I took were not even snapped. What scared me about that was what could have occured if I was in an enviromnent that would have let me go hundreds of feet deeper, if I really did dump my buoyancy and start dropping and had no bottom 5 feet deeper that could have been my last dive. As was I just hallucinated (sp) that I did those things.

In the back of my head I knew for that dive I didn't want to go below 120 feet, and I knew my turn pressure. I couldn't read yet somehow I never went below my target depth and did go up at my turn pressure, just not at the time I should have. I knew when I was starting to get narc'd but I didn't realize how quickly with depth it gets worse. My brain just stopped working for the most part. I've been told that you can get used to it, but my thoughts are why even risk it? I'm ok at 100' and so that's the deepest I want to go on air. Later on I may do some tech classes to use other mixes, but for air I'm setting the limit at which I will go. That limit is flexible by the way, I now know that once you start getting narc'd it can snowball on you getting worse quickly with only a few more feet.

For what it's worth, I'm in fair shape, do not smoke or drink at all. I was not sick or sub par in any way that day until I got narc'd, and I vow to you that I'm not going to place myself in that situation again. Once I start feeling it, that's it regardless of depth.

I prefer people to think I'm competant and do not make mistakes, I hate to admit to them and this is one I'd rather not tell. I told it because maybe it might help somebody else to think about it. The event really humbled and scared me.

Safe is safe only if you are in total control of the event, and if you're narc'd you are starting to lose control. Losing control is one way to die.