Deepest safe depth on air?

[Rick Inman]

I read last year that there has never been a recorded incident of a diver toxing on air above 218'

I think what Andy is trying to say is that, due to the nature of OxTox, it is difficult - if not in some cases impossible - to verify that OxTox was really the cause of an accident. So, if could have happened shallower without being validated.

 

[padiscubapro]

There is some other info that hasn't been added here..

so here is my input.

In the big bad years there were lots of deep air dives.. the record is over 450fsw, mine was 300.. None of the real deep air divers reported any symptoms under normal conditions.. I know at 300 I was fine until I started kicking hard, and then I got some mild ear ringing.. I never did do that again!!! I did have alot of air dives in the 200-240 range without any otox problems, my big issue was the narcosis.

Now the right gases are available and we know better, no one should be diving to these depths on air unless absolutely necessary and they understand the consequences..

WHy didn't all these people OTOX.. no one really knows, but its probably a combination of multiple thins.. Repeated exposures is one thing.. but the element that seems to make the most significant difference is the lack of helium and an abundance of n2..

Studies seem to indicate that the high narcotic loads of n2 at these depths and its depressing of the central nervous system is what is holding back the toxicty symptoms..

To add to this people on high helium mixes have experienced otox symptoms with much lower PO2 exposures, since helium acts like a central nervous system acclerator..

 

[matt_unique]

The safest depth depends on the person and relative circumstances. The max depth on air before exceeding 1.6 pp/02 is just over 218' (218' and change). As most everyone else has said, everyone experiences narcosis differently. Some people feel narced at 100', some people feel OK at 150'. The reality is you are narced at that depth on air, even though you may not feel it. I personally feel this martini affect when I descend below 140'. That seems to be the most common magic number for me.

You can also feel fine at a given depth one day, then very narced the next day at the same depth.

My personal limit is 160' on air. I would not go deeper until I'm certified in Trimix.

--Matt

 

[Gary D.]

Oh, right. Don't know what the gas was, but it shouldn't mater.

Nope, don't know if they have tested for tox on 21%.

When we did our O2 tolerance tests it was 100% flooded O2 at 60’ for 30 minutes at rest. There were many O2 tox hits at this depth.

After Apollo-One they started to use masks and eliminate chamber O2 flooding. What they do today I don’t know.

Gary D.

 

[Rick Inman]

When we did our O2 tolerance tests it was 100% flooded O2 at 60’ for 30 minutes at rest. There were many O2 tox hits at this depth.

After Apollo-One they started to use masks and eliminate chamber O2 flooding. What they do today I don’t know.

Gary D.

Every day people are recompresses at 60' on 100% (table 6) for a little more than an hour before decreasing the depth. I wonder how many people tox out?

 

[Diver0001]

I have heard from other divers of diving beyond 170' on air, and I'm of the opinion that oxygen toxicity would become a problem beyond that depth. My dive computer seems to agree with me. Is this correct? I've heard divers claim depths in excess of 200' on air alone.

O2 toxicity becomes a factor at about 220. Bigger problems are narcosis, which can start to significantly affect some peoples' functioning at about 100ft, the air supply you have to make such a dive and the decompression obligations you will incur.

R..

 

[Tavi]

That brings up another question. Would the folks on the thread here do a 170' dive in tropical waters on air?

Warm clear tropical waters, Yes, I'd go 170' on air.
Dark cold lakes, NO WAY......... Trimix for depths over 100'

 

[subaquaman]

Personally, I've never strayed outside the limits of my agency (PADI). I've completed their deep specialty course and as such am trained to 40m (~120ft). Given the right conditions (say the warm water example given), and the right planning I don't think I'd have a problem with extending my range. However, conditions here just don't warrant it.

The deepest site I have dived is a wreck lying in around 37m (~110ft) to the bottom. I've dived it a couple of times and haven't been noticably narked. However, I dived it once last year and had quite a scary experience. My buddy and I began our ascent along the shotline from the bow at about 31m (~93ft). We'd come up when my computer indicated 1min NDL remaining and my computer was on a conservative setting (I was using a Suunto Vyper), so we were well within limits. I had felt slightly narked just some anxiety (new buddy, cold temperature, it's also a dark gloomy wreck at the best of times) at the greatest depth. However at about 27m (~80ft) everything went dizzy. I couldn't read any of my gauges, they were completely blurred and I couldn't focus on my buddy, who was looking at his gauges and hadn't copped the problem. In the back of my mind I knew it was a form of narks and I needed to ascend. So I reached up and pulled myself up the shotline for a few metres. At about 23m (~69ft) everything focused again and all was back to normal.

I'm still not quite sure what it was but seeing this thread made me think about the cause of narcosis. I didn't want to hijack so I opened a new thread in medicine here.

Just my two cents....

 

[DA Aquamaster]

The lenght of time the high O2 exposure is experienced is a factor. The US Navy did some exhaustive research on extreme PPO2 exposures and basically found that most divers can tolerate amounts well over todays standard of 1.6 for breif periods of time. The farther past 2.0 you get the shorter the time. They also discovered that oxtox was very hard to accurately predict as there are multiple variables involved. (CO2 levels, exertion levels, individual physiology, acclimation to higher PPO2, etc.

The ability to tolerate high PPO2's for short periods is what lies behind 240-400 foot dives on air.

I also agree with what's been stated above that nitrogen, and the anesthetic affect it has at depth delay the onset of or minimiuze some oxtox symptoms and that the reduction of the affect with helium makes Oxtox a concern at lower PPO2's.

The use of O2 in a decompression chamber at a PPO2 of 2.0 is common. However the chamber is an air environment with the divers breathing from masks with 100% O2. The masks are normally held to the diver's face by the diver so if they feel the onset of ox tox symptoms, they remove the mask and take an immediate and unscheduled air break. If they experience oxtox the mask falls off on it's own. The critical thing here is that the diver is not going to drown as would happen most likely underwater if they convulsed in anything other than a full face mask.

 

[ChillyWilly]

I Was just reading a book on this stuff and according to research here is a quote.


"At or below 1.3 ATA, the onset of symptoms appears to be unlikely. At 1.6 ATA and above, diver can expect to suffer potentially life threatening OXTOX symptoms. Between 1.3 and 1.6 ATA is a crapshoot."

This is all based on research conducted, this depends a lot on how your body is that day. The efects vary from day to day, hour to hour. So if you stay below 1.3 ATA you are safe. In between 1.3 and 1.6, you could be at risk. So why risk it!!!