Exactly how deep is "Deep Air?"

[Cave Diver]

As anyone who has spent any amount of time on SCUBA forums knows, doing Deep Air dives is a hotly debated topic. Some say it's evil, some think nothing of it. Others feel the truth lies somewhere in between. One thing that is rarely defined though is exactly what "Deep Air" is.

The two references that I most commonly see are anything with an END greater than 100' or 200' or more. What does the term mean to you?

Note: This is not intended to debate the pros/and cons of deep air. There are plenty of threads for that already. This is more about defining where that line lies for individual divers.

Edit: for clarification, I'm interested in answers based on your personal assessment of narcosis and the point where you feel it adversely affects your ability to safely manage it.

 

[Luku]

Acute oxygen toxicity can occur by breathing an air mixture with 21% O2 at 66 m (216 feet) or more of depth.

I would think that would be a good starting point. Though I know plenty of people have been deeper than that.

 

[Cave Diver]

Acute oxygen toxicity can occur by breathing an air mixture with 21% O2 at 66 m (216 feet) or more of depth.

I would think that would be a good starting point. Though I know plenty of people have been deeper than that.

Good point on the toxicity. I edited to refer to a more subjective answer on narcosis.

 

[Superlyte27]

Acute oxygen toxicity can occur by breathing an air mixture with 21% O2 at 66 m (216 feet) or more of depth.

I would think that would be a good starting point. Though I know plenty of people have been deeper than that.

I agree
Back in the day, the Navy thought 320' was the limit. Obviously this didn't work really well. It was moved up to 218' and is at 218' today decades later. I'm ok above 200'. Around 220' I worry if this could be the time I take a hit. I have sat on Pure O2 for 30 minutes at 60'. I'm guessing my tolerance is a bit better than those who might not have passed an oxygen tolerance test, but I still worry when i'm at 220.

*edit* As far as narcosis goes...
Have you ever signed your name on the surface then signed your name at 200'? How about some basic math problems like 2+13= on the surface, then at 200'? It's kind of funny to see how people react. I've watched as people's signatures were completely unreadable. Some people couldn't even remember their names and certainly couldn't do the math problems. The fact is, people react differently. I'm not special, but I am one person who's signature is exactly the same both times. Once upon a time I ended up at 271' on air because of a malfunction beyond my control. My math would have suffered terribly. I've never been drunk before (because I don't drink), but I remember the feeling at 271' and remember thinking, "this must be what it feels like to be drunk". It's the only time I've felt that feeling. Oh, and I don't particularly care for it.

 

[MauiScubaSteve]

With regards to narcosis, my max depth to date is 146' (138' solo) and on those two dives I did not seem to be unsafely impaired either time; I came back up to average recreational depth with plenty of time and air! I really don't dive below 100' very often.

I really only join deep air conversations when they become "deeper than 80' with 80 cft of air" conversations.

 

[dumpsterDiver]

The explaination is bad. What depth does narcosis begin to be felt by me is one depth (for me maybe 160) and then you say OR what depth is too deep from a narcosis standpoint. I set my personal limit at 200 with maybe another 20-30 feet deeper in unusual conditions.

 

[Cave Diver]

The explaination is bad. What depth does narcosis begin to be felt by me is one depth (for me maybe 160) and then you say OR what depth is too deep from a narcosis standpoint. I set my personal limit at 200 with maybe another 20-30 feet deeper in unusual conditions.

Ok, hopefully the last edit clarifies it enough for everyone.

 

[UCFKnightDiver]

I agree
Back in the day, the Navy thought 320' was the limit. Obviously this didn't work really well. It was moved up to 218' and is at 218' today decades later. I'm ok above 200'. Around 220' I worry if this could be the time I take a hit. I have sat on Pure O2 for 30 minutes at 60'. I'm guessing my tolerance is a bit better than those who might not have passed an oxygen tolerance test, but I still worry when i'm at 220.

*edit* As far as narcosis goes...
Have you ever signed your name on the surface then signed your name at 200'? How about some basic math problems like 2+13= on the surface, then at 200'? It's kind of funny to see how people react. I've watched as people's signatures were completely unreadable. Some people couldn't even remember their names and certainly couldn't do the math problems. The fact is, people react differently. I'm not special, but I am one person who's signature is exactly the same both times. Once upon a time I ended up at 271' on air because of a malfunction beyond my control. My math would have suffered terribly. I've never been drunk before (because I don't drink), but I remember the feeling at 271' and remember thinking, "this must be what it feels like to be drunk". It's the only time I've felt that feeling. Oh, and I don't particularly care for it.

You know studies have shown (chamber experiments though I'd have to go find the study I read) that toxing is extremely random and varies greatly from day to day. I don't think one tolerance test would do you much good.

 

[BHB ScubaTroll]

I generally steer clear of threads like this due to the toxic nature of the debate that usually happens after a few posts. The only reason I am posting is because CD has asked the question, and I suppose there will be quick/direct moderation when it goes off topic to "beatings/pile-ons"

This is a very difficult question, and is very controversial based on each divers training (time period) and experience. I was first certified for 130' as the sport diver limit. Others have been certified under different limits, both deeper and shallower based on when they were certified... also years of testing and experience (based on EAN21).

I have realized narcosis at 60' and beyond depending on many factors in the past. I have not felt narcosis at 30', but I do understand that it is there... But, the subjective question here from my perspective is "at what depth do you believe deep air will assist you in making proper decisions in a timely manner?"

I will admit that my deepest dive on EAN21 was to 255' with a plan at 165' in Cozumel. At the time I was recently certified as an instructor, in shape, and I was diving with a group lead by another instructor.

The plan was for the "group supervised by the lead instructor" to stay with the DM, and the lead instructor and I would dive our plan to 165'... At 145', I checked my gauges, with a slight buzz in my head... I began to level out... I looked down and saw fins only. At 165' my head was ringing and it was all I could do to concentrate on my gauges and my bottom time. I was on the ledge and I just saw the fins of the other instructor...

This is before dive computers, and I knew I had my dive tables in my BC, so I followed in an attempt to catch those fins... I made a decision right at that moment that I would not go beyond 240' (PPO 1.6)... I caught his fins at 255'. He turned to me and indicated it was time to go deeper... I shook my head no, and gave him the thumb up... He turned and started down. I grabbed his fin and began ascending via kicks upward. He tried to kick away, but I had his leg locked under my arm...

Shortly, he turned to me and gave me an "OK". I stopped and let go of his fin to see what would happen (I have no idea what my gauges read at this time, my only purpose was to ascend at a safe rate of speed, following the wall up)... But, as I let go my only thought was "If he starts down again, he is on his own"... I remember feeling relieved when he started upward... My thought "OK, we blew our plan... now the rest of the dive is a hang when we get there"...

We ascended to where the others were drifting at 90'... He stayed with that group and I kept ascending, since my tables didn't include 255', I did an extended stay at 20' and the rest of the tank (to 200 psi) at 10'... I dove the next dive to 55' and kept it conservative. The remainder of the week, I took control of the dive group and no one dove deeper than 130'... The lead instructor for the group I was with was in a wheelchair after day two, and he blamed it on a Cozumel hooker

All dives after that have been 200' or above. I regularly dive 130' and above...

Based on my previous training and experience, the fact I am much larger than I was at 21... and my exercise regimen... I would say my personal idea of "at what depth do you believe deep air will assist you in making proper decisions in a timely manner based on narcosis" at the PPO... 1.6... Or what ever emotional state I am in at the time I make the dive to that PPO...

Basically... It changes with every single dive you make!

 

[Luku]

Edit: for clarification, I'm interested in answers based on your personal assessment of narcosis and the point where you feel it adversely affects your ability to safely manage it.

That's the problem with narcosis, everyone feels just fine, most people will just say been to 100+ felt great no problems. I doubt you will find a diver here who will say I couldn't function and had to be rescued. Those who have been rescued don't remember being in trouble because once they get to about 100' everything is fine again. I've seen it happen and had to drag people back up.