Deepest safe depth on air?

[BrianV]

Excuse the relative newb questions I'm going to ask, but I'm honestly surprised at some of the depths you guys list. I'm curious:

1) For those who do 150-175, what kind of bottom time are you looking at, and how did you ascend after (any deco)?
2) For those who did 175-250, what was your bottom time and deco?

I'm also surprised to hear of people having Narc issues at as low as 70' or even 120' for that matter. I've only gone to 87' and had no problems at all. I'm taking AOW soon so I imagine we'll be going 90+, but now I'm somewhat afraid to go on a dive on vacation that might be 100+. I never plan on going below 130, but now I question whether I even want to go that far.

Thanks

 

[wedivebc]

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!!!

What book are you getting these pearls of information? Most training agencies support PPO2 exposure in the 1.4-1.5 range for the working portion of the dive and 1.6 for the deco portion. I doubt they would be so supportive if it was "a crapshoot"

 

[Hank49]

I did a dive to 65 meters then went up to about 50. I was inside a little overhang and thought, "wow, what a pretty reddish color everything is". After the dive, no one else said they saw red. It was like looking through red tinted sunglasses. I was told it may have been the first effects of O2 tox. I ascended a bit and it went away. I've done 50 or so other dives deeper but that was the only time that ever happened.

 

[Diver0001]

Excuse the relative newb questions I'm going to ask, but I'm honestly surprised at some of the depths you guys list. I'm curious:

1) For those who do 150-175, what kind of bottom time are you looking at, and how did you ascend after (any deco)?
2) For those who did 175-250, what was your bottom time and deco?

I'm also surprised to hear of people having Narc issues at as low as 70' or even 120' for that matter. I've only gone to 87' and had no problems at all. I'm taking AOW soon so I imagine we'll be going 90+, but now I'm somewhat afraid to go on a dive on vacation that might be 100+. I never plan on going below 130, but now I question whether I even want to go that far.

Thanks

Assuming a leisurely descent along a sloping bottom the the Suunto computer I have will show something like a 3 minute NDL by the time you get to 150ft. Apart from the silliness of being there at all on air, all dives this deep should be treated like deco dives.

As for your other question, if you get the chance some time, make a dry dive in a recompression chamber. You can clearly feel the narcosis hitting you at 80ft. Somehow being in a chamber makes it easier to feel it but I assure you that under water it's there at the same depth.

R..

 

[do it easy]

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?

I've heard that the chances of oxtox in a dry environment (like a chamber) are less than in a wet one (like underwater). The doctor who told this to me said that the reasons for this difference were not yet understood.

 

[Nemrod]

I have been 235 on air and over 200 feet a couple of other times and over 150 bunches. Now that I am older and wiser I do consider 130 feet the max and 100 feet the "practial" limit in terms of bottom time. My max depth last year was 135 feet but a group of vintage divers I was with on another dive hit 190. I did not accompany them because I felt a bit off and the water was cold and I am a coldaphobic etc etc.

I do not recall any unusual effects other than the air had a metallic taste, a biting sort of thickness to it. There are so many things going on and a rigid time profile that there was not much time for me to get into my "feelings". At the time of that dive I was in superb physical condition and had just completed a marathon. My opinion, only seasoned, physically fit divers should exceed 130 feet. N

 

[Mverick]

I've noticed narcosis as shallow as 65feet.

Think of it like drinking. When you see the girls who drink 2 drinks and are laughing and acting a little goofy. But keep telling you they are fine. More drinks and it gets worse. But at only 2 drinks there were effects... That they really didn't notice.

You might not notice it. But it's there.

Also, I've seen drunks that could drink a case of beer and walk and talk a little slurred. But could easily funtion. Because they've done it a thousand times. But if something happens unusual. Like someone pulling out in front of them. Wham....

 

[wardric]

Excuse the relative newb questions I'm going to ask, but I'm honestly surprised at some of the depths you guys list. I'm curious:

1) For those who do 150-175, what kind of bottom time are you looking at, and how did you ascend after (any deco)?
2) For those who did 175-250, what was your bottom time and deco?

I'm also surprised to hear of people having Narc issues at as low as 70' or even 120' for that matter. I've only gone to 87' and had no problems at all. I'm taking AOW soon so I imagine we'll be going 90+, but now I'm somewhat afraid to go on a dive on vacation that might be 100+. I never plan on going below 130, but now I question whether I even want to go that far.

Thanks

I'm looking at a study right now stating that narcosis can have effects as shallow as 30 ft. You had no problems at 87 ft because... ... you had no problems. Even if you dont feel "drunk" or paranoid or other feelings, it's there. at depth, you get much slower in your thinking and acting process, you will take a lot more time to identify a situation and act accordingly. that is where training and experience are usefull and help lower the reaction time that is so important in certain situations.

 

[vbcoachchris]

I use air at the surface, I find it to work very well there. From 0 - 100 use 30-32.
Add 30% He and it will lower the "Narced" feeling. Those who say they don't feel narced at 70 ft are narced, so don't trust their judgement.

 

[FloppyFoot]

Silly question, but are the very deep divers (600 fsw and deeper) using gas blends with O2 content below 21%? I haven't gone the tech route but was wondering about this the other day.