Oxygen Toxicity risk with Nitrox?

[BlueTrin]

@Fishdip agree, I doubt he knew what was his PPO2 when he decided to bend the rule and go to a different depth.

Personally my main issue, is that not only he broke the rule, but he did it without a sanity check, he just did ‘because others did’, which is very different from having thought of the consequences of breaking the rule.

I.e. it’s different from saying “I went to PPO2 1.6 for a couple of minutes and knew the depth for 1.6, I did it because I wasn’t exhausted and very relaxed”

 

[admikar]

On most liveaboards, going into deco will keep you out of the water for a day or two. Better to not exceed your MOD, and to not exceed your NDL.

How can they tell if I had few minutes of deco? My Perdix will not show no-fly time and I can just muck around for few minutes to clear deco

 

[BlueTrin]

How can they tell if I had few minutes of deco? My Perdix will not show no-fly time and I can just muck around for few minutes to clear deco

They can go in your dive log, you’ll see a red line for your stops, this is from the app, but does the computer show the same when viewing the log? (don’t have my computer on me)

 

[Belzelbub]

How can they tell if I had few minutes of deco? My Perdix will not show no-fly time and I can just muck around for few minutes to clear deco

The no-fly time is useless to determine if a dive was deco or not on most computers. My Garmin will likely switch between 12 to 24 hours on the display depending on the dive parameters. NDL remaining or Deco is one factor, but not the only one, so if my computer displayed 24 hours, that would not necessarily be an indicator that the dive was a deco dive. Since many computers default to 24 hours after a dive, no-fly time is useless as a basis for determining if the dive was deco or no-stop.

I don't have my Shearwater with me, but do have my Garmin. The Garmin log doesn't seem to indicate if the dive was No-Stop or Deco, all dives on this are No-Stop, so I'm not sure if the depth profile displays the ceiling or not. The log does include ending SurfGF, but that's the closest I could find that would indicate if there may have been a violation or not.

As was mentioned above, I believe the dive op looking for no-fly was just to try to win an argument. Probably betting on the fact that the diver may not fully understand the information being displayed. Very underhanded on their part if this was indeed the case.

 

[admikar]

They can go in your dive log, you’ll see a red line for your stops, this is from the app, but does the computer show the same when viewing the log? (don’t have my computer on me)

View attachment 753026

Yes it does, but they will have to give me good reason to be allowed to go into my dive logs.
Again, I am not talking 20+ minutes of deco, but few minutes, so how can they tell if I was in deco or not?

 

[BlueTrin]

Yes it does, but they will have to give me good reason to be allowed to go into my dive logs.
Again, I am not talking 20+ minutes of deco, but few minutes, so how can they tell if I was in deco or not?

There is no other way than by looking at your logs.

I don’t think they will care if you happen to have 2-3 mins of deco that cleared on the way up because you rode the NDL …

If they happen see your current deco while you are on the boat with your Shearwater, you may want to have a trip to the nearest chamber

 

[boulderjohn]

He said insurance won't cover me and he would not go to that depth with Nitrox to save a drowning diver.

I have never heard of that. Look at your policy.

Is it true that there are no warning signs before toxicity kicks in and you experience the effects?

The warning signs should have been part of your nitrox course. They may or may not occur.

 

[boulderjohn]

Way too many people have died as a result of exceeding their gas's MOD. Plan your dive and dive your plan.

Can you supply some sort of an official estimate on this for NDL diving?

I know of many cases with technical diving, but I don't believe I have ever heard of a single one in NDL diving. I would like to see some examples the "way too many people" if you can find them.

In the technical diving cases I know, we are not talking about someone going to a PPO2 of 1.55 for 4-6 minutes. We are talking serious MOD violations, often caused by the diver thinking he or she had a different mix than reality. In those cases, the toxicity came after significant time. Here are some cases I know of. I am writing these from memory, and some of the details may be a tad--but only a tad--off.

• A diver broke his foot and could not dive for several months. When he was ready to dive again, he took his double tanks to a wreck (Hydro Atlantic) with a deck at 150 feet/45 meters and about 170 feet/52 meters to sand. He did not check the tanks because he was sure they had air, but they had 36%. His buddy told me it took about 20 minutes before he toxed.
• A cave diver used a tank that was clearly marked as having pure oxygen for a dive to 100 feet. He told his friends he had filled it himself, so he knew it had air instead of oxygen. He refused to test it. I am not sure how long he was diving on pure oxygen at 100 feet before he toxed.
• A cave diver was supposed to leave a decompression bottle with 50% at a 70 foot staging area and take a different one more appropriate for 200 feet. He left the deep bottle at the staging area and took the 50% to 200 feet. I don't know how long he was diving at 200 feet on 50% before he toxed.

 

[theduckguru]

Sounds like a really dumb practice especially on a liveaboard when you are diving a lot.

 

[L13]

In the technical diving cases I know...

Thanks for incident info!