Toxicity: what is the limit of oxygen tolerance for a human over several days?

[oneQ]

(that is, the partial pressure of oxygen before oxygen toxicity begins)

Hypothetically, for both pulmonary tolerance and central nervous system (CNS) tolerance, assume a dive-related event were to occur for 1 week (7 full days) in a pressurized system, what is the maximum partial pressure of oxygen that could be tolerated by the diver during that time just before oxygen toxicity is induced?

I'm seeing studies of high partial pressures (140-160 kPa) for SHORT-TERM duration studies, but what partial pressures are lethal for LONG-TERM durations?

 

[Thalassamania]

You can take a ppO2 of 0.5 indefinitly.

 

[pittyyofool]

I remember hearing of studies that NOAA and the US Navy did in this. For the effects of Nitrogen and oxygen saturation over extended periods of time. I am not much help but it gives you somewhere to look.

Where is a Saturation diver when you need one?

 

[Van Isle]

My TDI tables give a 24 hour limit of 720 minutes per/24 hr period for O.6 PO2...

PO2 of 0.5 can be taken "indefinitely" according to NOAA. So roughly air at pressures not greater than 40 fsw.

Health problems have been noted at a PO2 of 0.21 after exposures longer than 78.1 years in greater than 66% of the US population.

 

[Thalassamania]

I remember hearing of studies that NOAA and the US Navy did in this. For the effects of Nitrogen and oxygen saturation over extended periods of time. I am not much help but it gives you somewhere to look.

Where is a Saturation diver when you need one?

Right here, and I gave you the answer already, 0.5!

 

[Web Monkey]

Hypothetically, for both pulmonary tolerance and central nervous system (CNS) tolerance, assume a dive-related event were to occur for 1 week (7 full days) in a pressurized system, what is the maximum partial pressure of oxygen that could be tolerated by the diver during that time just before oxygen toxicity is induced?

O2 Toxicity is variable between individuals and conditions and not precicely predictable.

Terry

 

[Thalassamania]

O2 Toxicity is variable between individuals and conditions and not precicely predictable.

Terry

Yes, but 0.5 ppO2 is the cutoff for a saturation system, that's why Aquarius is at a storage depth equivalent to 2.5 ATA.

Here's a table for O2 exposures:

ppO2 Max Exposure ​

0 death
0.1 death
0.2 indefinite
0.3 indefinite
0.4 indefinite
0.5 indefinite
0.6 720 mins
0.7 570 mins
0.8 450 mins
0.9 360 mins
1.0 300 mins
1.1 240 mins
1.2 210 mins
1.3 180 mins
1.4 150 mins
1.5 120 mins
1.6 45 mins
1.7 10 mins
1.8 2 mins


Saturation Divers (or astronauts) must have their ppO2 kept within 0.20-0.5bars.

 

[Meng_Tze]

your 'indefinite' ratings need to be capped. In the USA this is 78.1 years.

 

[Web Monkey]

Yes, but 0.5 ppO2 is the cutoff for a saturation system, that's why Aquarius is at a storage depth equivalent to 2.5 ATA.

It sounded like the OP was looking for some sort of well-defined hard limit where on one side of the line, everything is OK and on the other side is O2 Tox.

Terry

 

[Thalassamania]

Above 0.5 is considered to be that line, the higher it goes the faster it'll get to you. We do not store people for long periods of time above 0.5. Why is that so hard to understand?