How did old-school deep air divers avoid ox tox hits?

[ianr33]

Low O2 requires around 100ft and then it is safe

Huh??

 

[AfterDark]

Huh??

I think he means low PO2 at the surface may get to a breathable % after 100fsw. Similar to the PO2 of air approaching a toxic % after a 132fsw

 

[HowardE]

The Britannic dives as I recall were with triples and quads 72s/80s filled with different blends. Once below 10th most blends are safe. Low O2 requires around 100ft and then it is safe

Divers on the Brittanic Expeditions also used rebreathers.

As for the low O2 percentages... even 10% O2 is breathable to at as shallow a depth as 33 fsw or 2 ATA. Do the math. .1 (fO2) * 2 (ATA) = .2 ppO2. We need a minimum of .16 ppO2 to sustain life.

The MOD for 10% O2 is 495 feet.

 

[AfterDark]

Divers on the Brittanic Expeditions also used rebreathers.

As for the low O2 percentages... even 10% O2 is breathable to at as shallow a depth as 33 fsw or 2 ATA. Do the math. .1 (fO2) * 2 (ATA) = .2 ppO2. We need a minimum of .16 ppO2 to sustain life.

The MOD for 10% O2 is 495 feet.

Howard was rebreather technology that advanced in 1976? I know its been dived since 1976 with rebreathers but this was specifcally about the Cousteau dives. It must have been a mad rush to the depths with their mix!

 

[HowardE]

I was referring to the later Brittanic expeditions with John Chatterton, etc.

Sent from my totally hacked and customized android phone using Forum Runner

 

[ianr33]

I think he means low PO2 at the surface may get to a breathable % after 100fsw. Similar to the PO2 of air approaching a toxic % after a 132fsw

Kind of depends on what the PO2 at the surface actually is though dontcha think?

To only be breathable at 100 feet the % O2 would need to be around 5% (pO2 of 0.2 at 99 feet)
MOD of a 5% O2 mix is around 900 feet. That's a little on the deep side for most people.

Most hypoxic mixes. (Those used by 99.9999999% of divers) will be breathable at 20 or 30 feet.

 

[AfterDark]

Kind of depends on what the PO2 at the surface actually is though dontcha think?

To only be breathable at 100 feet the % O2 would need to be around 5% (pO2 of 0.2 at 99 feet)
MOD of a 5% O2 mix is around 900 feet. That's a little on the deep side for most people.

Most hypoxic mixes. (Those used by 99.9999999% of divers) will be breathable at 20 or 30 feet.

I didn't mean his numbers were correct, just the concept. I think Howard nailed it earlier.

 

[Spazzy]

Yes the 1.4 and 1.6 limits are conservative.

 

[Jared0425]

Yea I can't tell you exactly what they used. I'm no expert in mixed gases. Britannic at that time was the one of the deepest dives by scuba equipment. I will talk to a person that might know what they used.

 

[AfterDark]

Yea I can't tell you exactly what they used. I'm no expert in mixed gases. Britannic at that time was the one of the deepest dives by scuba equipment. I will talk to a person that might know what they used.

In another thread on SB someone posted the French at that time used 2.0ata P02 as a safe limit, which probably holds the answer. They described it as heilox which infers to me only helium and O2 was used. Big ones those guys had , yes indeed.