What's your PO2?

[Kern]

Hyperoxic mixes 1.2 - 1.3
Normoxic mixes 1.4
Air 1.4
Deco 1.6

I seem to be more sensitive to oxygen in hyperoxic mixtures in cold water and current.

Do you not teach PSAI's signiture, narcosis management course at all? Or do you just not teach beyond a level that would increase you ppO₂ above 1.4? Or do you go somewhere with low current & warm water & exceed ppO2 1.4?

 

[Trace Malinowski]

Do you not teach PSAI's signiture, narcosis management course at all? Or do you just not teach beyond a level that would increase you ppO₂ above 1.4? Or do you go somewhere with low current & warm water & exceed ppO2 1.4?

No, I do not teach the PSAI narcosis management program.

 

[nhebrant]

1.4 working (although i have gone to 1.6 no probs) and 1.6 for deco.....
All depends on your body what can be tolerated. BSAC allows up to 1.8 I believe....

3.0 is where everyone will convulse, below that just depends on what you can tolerate and how you feel. Although said that Im pretty sure that recreational dive computers (suunto and mares for eg) do not allow anything above 1.6.

rgds

 

[String]

All depends on your body what can be tolerated. BSAC allows up to 1.8 I believe....

No, BSAC are 1.4 although they've fiddled it to fit their 35m qualfication and allow "32% nitrox to be dived to 35m meaning 1.44 for no-stop dives" just as a fudge. They only allow 1.6 deco at 6m so its 1.4 even for deco below that. They're the most conservative (ok, backward) i cant think of ignoring the world-wide norm.

 

[Tortuga68]

3.0 is where everyone will convulse

What are you basing that statement on?

 

[peterbj7]

I don't know that that's true, but I am told by a nurse that 3.0 is the highest they use in pressure chambers in hospitals, at any rate in the UK. At that level they strictly restrict exposure to reduce the likelihood of convulsions, which although not lethal are pretty discomfiting for the patient.

I also believe that in wartime missions were planned with the pO2 going up as far as 3.0, even though in peacetime exposure was limited to 2.0.

 

[kanonfodr]

I also believe that in wartime missions were planned with the pO2 going up as far as 3.0, even though in peacetime exposure was limited to 2.0.

I highly doubt that missions are ever planned to hit a PO2 of 3, it is likely only a contingency since most units performing underwater ops of a combat nature don't like being risky with the things they can control. Getting above 2.0 is probably one of those risks, no need to risk someone dying before you even met the enemy. But if the choice is either be discovered or momentarily go deep and jack up the PO2, they would most likely go deep and risk it.

Peace,
Greg

 

[FireInMyBones]

A recent discussion in another thread highlighted the difference of opinions among divers on an acceptable PO2 for gas planning. Over the years, I've seen a shift in the recommended max PO2.

I'm a bit curious about the difference in personal attitudes and training on the limits that people use in planning the working portion and deco portion of their dives.

For working portion, do you normally prefer 1.0 or less, 1.2, 1.4, 1.6, or something else?

For the deco portion of your dives do you normally prefer to keep your PO2 at 1.4, 1.6, or something else?

What adjustments (if any) do you make for adverse conditions? (strong current, cold water, etc.)

What is the main driving force in your choices?

When I first took Nitrox, I ran a 1.6 at all times. After tech training: 1.2 working, 1.4 deco gases (not O₂), 1.6 for O₂.

If it is a new dive or conditions are a little wild, I drop my working to no more than 1.0

 

[Tortuga68]

I highly doubt that missions are ever planned to hit a PO2 of 3, it is likely only a contingency...

There's a book Amazon.com: ABOVE US THE WAVES: The Story of Midget Submarines and Human Torpedoes (Pen & Sword Military Classics) (9781844154401): C E T Warren and James Benson: Books which talks about the British 'Charioteers' and their missions; it's a good read

Before and in the early years of WW2 the Royal Navy exposure limits for 100% oxygen were 2 hours at 15m (PPO2=2.5) or 30 minutes at 27m (3.7). During the war, as a result of Kenneth Donald's research (spurred by the number of OT incidents), it was revised to 7.6m (1.76) with no time limit specified

Further research by the USN in the 1950s set a time limit for 7.6m of 65 minutes, with a maximum exceptional exposure limit of 14m (2.36) and 15 minutes. This wasn't revised until the 1970s

So yes missions were planned over 2.0 and no not everybody toxes when they hit 3.0