diving air to 210 feet??

[drbill]

Although I have not ventured to 210 ft on air, I have done a number of dives to 200 ft on it. It is not something I recommend to anyone, but based on my experience it is possible to be at those depths at least for short periods of time and function reasonably well mentally. I judge that based on my ability to locate, frame and follow marine life that I video. Obviously I am narc'ed at that depth, and should something happen my response time would undoubtedly be longer.

I should also add that I spent some time diving to deeper and deeper depths (gradually, usually 10 ft intervals) to assess my response to narcosis before attempting to reach 200 ft. My bottom time at maximum depth is generally very short (under 5 min) since I use it as a starting point to work upslope in search of deeper critters to document.

Given my current gear configuration, I no longer do such deep dives and limit myself to about 170 ft. If I needed to return to depths in the 200 ft range, I would return to a more appropriate tank set up than I currently dive.

 

[The Surly Mermaid]

100% O2 is not toxic at 20', in fact that is the perfect depth for it to be used as a deco gas as you have a 1.6 PO2.

I said roughly 20 feet, and actually 20 (fsw) is just over 1.6 PO2. From everything I have studied O2 tox is possible at 1.6.. If you know of studies that states that O2 tox is not a possibility at 1.6 please let me know. Would like to read up on it.

 

[ianr33]

20 feet is the totally standard depth to start deco on O2.

Obviously O2 tox is a possiblity at 1.6 but provided that you are not working hard and do not stay on it too long it is very unlikely. I would not use O2 at 20 feet for longer than 15-20 minutes without taking a break for 5 minutes to backgas.

Starting O2 at 20 feet rather than 10 feet will significantly shorten deco times.

 

[DA Aquamaster]

I said roughly 20 feet, and actually 20 (fsw) is just over 1.6 PO2. From everything I have studied O2 tox is possible at 1.6.. If you know of studies that states that O2 tox is not a possibility at 1.6 please let me know. Would like to read up on it.

Oxtox is possible at less than 20 feet in terms of a CNS hit and total exposure can be an issue even at the surface if you are on O2 long enough, but a PPO2 of 1.6 is pretty much standard for deco purposes. On the working portion of the dive you back it off to 1.4 or even 1.2.


------

A dive to 200' on air is deceptively easy. With a decent real world SAC around .6 for the bottom portion of the dive and .4 for the deco portion, you can do 20 minutes at 200' on a set of doubles 80's and have 1/3rd in reserve - so gas volume is not really the problem (and that is why many techical divers discourage OW divers from using doubles - that much gas can get you in serious decompression trouble.)

It would require 40 minutes of deco starting at 90' with DPlan (a bubble gradient model) with 6 minutes on 100% O2 at 20' and 9 minutes of O2 at 10 ft.

However with no O2 available you'd require 128 cu ft versus 106 cu ft of air and would require more time at the shallow stops with 64 minutes of deco total, 13 minutes at 20 ft and 26 minutes at 10 ft.

If you blow off that much deco, you are going to get seriously hurt if you are lucky and very dead if you are not, so redundant equipment and proper training is essential.

 

[flw]

I said roughly 20 feet, and actually 20 (fsw) is just over 1.6 PO2. From everything I have studied O2 tox is possible at 1.6.. If you know of studies that states that O2 tox is not a possibility at 1.6 please let me know. Would like to read up on it.

The original experiements on oxygen were on military 'volunteers' and its hard to put a linear progression on o2 hits -all it means is that 1.6 is the level at which,when on deco, you are unlikely to fit- although on long stops taking breaks is necessary on a low po2gas. Although it isn't particularly bed time reading Oxygen and the Diver by Kenneth Donald ( think its out of print) is well worth a read.
Historically I think a pO2 of 2 was used for deco by some organisations

 

[Hallmac]

As much as I hate to admit it now, I once made a dive to 250' on air. 2 minutes on the bottom, no deco gas, and used a single 80 cubic foot aluminum for the whole dive.

My buddy ran out of air during the ascent. I still have the print out from the cobra someplace around here. It can be done, just not smart.

 

[tc]

In chamber treatments we take the patients up to 2.8, 60 fsw on 100% O2. But remember, patient is lying down, warm and hopefully relaxing.

The problem with predicting where someone will tox on O2 is that in testing even individuals change from day to day.

 

[Walter]

I have my doubts as to the voracity of his claims.

Why? Was he bragging? or did it come up matter of factly in the conversation?

Is it even possable to go to 210 feet on air??

The record on air is well over twice that depth.

I would think that bad things would happen at those depths.

They certainly can, but they do not happen automatically.

What do you guys think?

About?

 

[ZenDiver.3D]

Yes, it is possible. Cousteau dove at 100 meters (330 feet) with air.

Talking about Cousteau.... True, but Cousteau was the anomaly. Do you know how many of his dive buddies died of dcs with him? Of the top of my head, it was over 30. He had an amazing physiology.

 

[vintagediver]

"100% not toxic @ 20' "?
"O2 is toxic for all living things," at all depths regardless of pressure....
"for if they breath it they will one day die"!