safety stop on 80% O2.

[hecker-the-wrecker]

We do our safety stop on 80% O2 (at 20ft.) Last weekend as our stop was coming to an end, the boat started to drag the anchor. I switched back to my tank of 36% and my dive buddy didn't, he continued on 80% O2. We stayed at the same depth, and grabbed the anchor line and swam it to a point where it could be clipped to the bouy line.(approx 10 min) I was concerned he stayed on the 80% while under exertion.He said the partial pressure did not change and there was no danger. Was there any danger of working hard at 20ft on 80% O2? :06:

 

[IceDiverInCA]

We do our safety stop on 80% O2 (at 20ft.) Last weekend as our stop was coming to an end, the boat started to drag the anchor. I switched back to my tank of 36% and my dive buddy didn't, he continued on 80% O2. We stayed at the same depth, and grabbed the anchor line and swam it to a point where it could be clipped to the bouy line.(approx 10 min) I was concerned he stayed on the 80% while under exertion.He said the partial pressure did not change and there was no danger. Was there any danger of working hard at 20ft on 80% O2? :06:

You had EAN36 as your backgas and your 20ft stop was just a safety stop, not a mandatory deco stop. Why are you even bothering with EAN80 to begin with?

 

[boomx5]

Why are you even bothering with EAN80 to begin with?

That's my question also.

 

[matt_unique]

Just a thought - maybe a looong dive within pp02 depth limits for 36% backgas?

 

[hecker-the-wrecker]

You had EAN36 as your backgas and your 20ft stop was just a safety stop, not a mandatory deco stop. Why are you even bothering with EAN80 to begin with?

We use it as part of our dive plan if it's a deco stop or not. It seems pretty important to be familiar with your configuration, especially under a deco obligation. So rather than changing our configuration, it's more like "practice" with our setup under a non-mandatory stop.(It is a more efficient method of offgassing nitrogen on repetitive dives) But enough about me, did anyone bother to read the question???

 

[Hyper-limits]

We do our safety stop on 80% O2 (at 20ft.) Last weekend as our stop was coming to an end, the boat started to drag the anchor. I switched back to my tank of 36% and my dive buddy didn't, he continued on 80% O2. We stayed at the same depth, and grabbed the anchor line and swam it to a point where it could be clipped to the bouy line.(approx 10 min) I was concerned he stayed on the 80% while under exertion.He said the partial pressure did not change and there was no danger. Was there any danger of working hard at 20ft on 80% O2? :06:

80% at 20ft give you a 1.28 PO2, I would say that a pretty good safety margin, as long as he stay at 20ft they shouldn't be any problems.

 

[hecker-the-wrecker]

80% at 20ft give you a 1.28 PO2, I would say that a pretty good safety margin, as long as he stay at 20ft they shouldn't be any problems. How hard were you working?
or were you holding the anchor line as it was dragging.

We dragged the boat back against the current and wind to clip the two lines together. It's an alumminum chambered boat (like a stabey craft.) We were working pretty hard. Plus it was the second dive of the day on the shipwreck "america" in lake Superior. Although the water temp was a brisk 37f, we had on drysuits.

 

[Hyper-limits]

We dragged the boat back against the current and wind to clip the two lines together. It's an alumminum chambered boat (like a stabey craft.) We were working pretty hard. Plus it was the second dive of the day on the shipwreck "america" in lake Superior. Although the water temp was a brisk 37f, we had on drysuits.

I guess you did the right thing by going back to your back gas. After all it was a safety stop so it is better being safe than sorry.

 

[wedivebc]

We dragged the boat back against the current and wind to clip the two lines together. It's an alumminum chambered boat (like a stabey craft.) We were working pretty hard. Plus it was the second dive of the day on the shipwreck "america" in lake Superior. Although the water temp was a brisk 37f, we had on drysuits.

As hyper-limits mentioned you had a po2 less than 1.3 on 80% you didn't state what depth you were spending the rest of you profile but the NOAA CNS exposure table allows 3 hrs at that exposure.
Were you tracking your CNS clock?
_______________________________

 

[jagfish]

It seems to me he is asking more about a sudden oxtox hit due to the exertion.

My guess is that's pretty hard to predict at what level of exersion from what PpO2 people are at risk.