Nitrox table vs computer question
- Thread starter Lizard Leg
- Start date
Please register or login
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
- Ability to post and comment on topics and discussions.
- A Free photo gallery to share your dive photos with the world.
- You can make this box go away
Paleface
Contributor
Download V-Planner, I have it on my Droid. You can punch in all the variables you want to look at. In real life you dont know how your body is going to react to things. I have dove to 1.5 PPO2 with no ill affects. 32% @ 122' = 1.5 PPo2 Best mix for 120' is 30% @ 1.4 PPO2 I was taught baby steps 
OP
Lizard Leg
Contributor
Thanks for all of the info guys. This was just a math exercise at this point. If we dove nitrox on this dive, then we were doing 30%, but was wondering how you would plan it at a shop/location where all that was available was 32/36.
have you attempted to contact them (Alberto is a member here under the username DiveNav - if i remember correctly)? He has always been helpful.
OP
Lizard Leg
Contributor
Not yet, I just did the dive based on air, but at the EAD from my calcs for each step in the dive profile.
the other thing is he may have your computer model in the simulator, making it "closer to what you may see"....
Well, risk assessment is a balance between "How likely is this event to occur?" with, "How dangerous is the event if it occurs?" The likelihood of O2 toxicity by exceeding the ppO2 of 1.4 for a period of time is proportional to the degree to which you exceed it, and the length of time you do so -- but one of the scariest things about ox-tox seizures is that they are so horribly unpredictable between people, and even with a single person on different days. One of the most frightening things in my Rec Triox class was a table that summarized a variety of experiments done by different groups investigating oxygen toxicity. It impressed the dickens out of me. So the answer to the first question is that nobody can tell you, really, what the risk of a seizure is if you do 45 minutes of bottom time at a ppO2 of 1.5, but it isn't zero, and it's almost certainly higher than staying shallower or using a lesser mix.
The second part of the question is, "How dangerous is the event?" The answer to that is that almost all oxygen toxicity seizures that occur underwater are lethal. There have been a couple of documented survivors, both with highly trained buddies who happened to be focused on the diver at the moment the problem occurred, and who executed the salvage procedure flawlessly. I wouldn't count on that, especially during the average recreational dive.
So you have an outcome whose likelihood is uncertain and variable but which will almost certainly be lethal if it happens -- I don't know about you, but that's enough to make me want to avoid the risk. I dive conservative ppO2s.
The second part of the question is, "How dangerous is the event?" The answer to that is that almost all oxygen toxicity seizures that occur underwater are lethal. There have been a couple of documented survivors, both with highly trained buddies who happened to be focused on the diver at the moment the problem occurred, and who executed the salvage procedure flawlessly. I wouldn't count on that, especially during the average recreational dive.
So you have an outcome whose likelihood is uncertain and variable but which will almost certainly be lethal if it happens -- I don't know about you, but that's enough to make me want to avoid the risk. I dive conservative ppO2s.
windapp
Contributor
WeldonDowd
Contributor
I just finished a dive where I had a tank of ean35 and if I used it at the planned depth would push my ppO2 to 1.5. Luckily I also had a tank with ean33 on board so I got to do the dive as I wasn't going to leave my 1.4 comfort zone. But during that timeframe I was wondering why 1.5 and even 1.6 are options on my computers and tables. Who is diving those levels? Is it safe? I didn't mean to hijack this thread but thought it went along with or at least added to the original post.
this is where the class would be useful, mainly to tell you what the risks are with pushing the MOD of a certain mix........ox tox like what has been mentioned is pretty f'n dangerous and pushing O2 limits isn't generally a good idea. For recreational dives on 32%, id keep the dive plan to 1.4ata or 111ft, its not worth the risk to push the PPO2......that being said i have no problems being at 1.6 or a bit higher for a moment.....but I sure as **** would not plan a dive like that.
There are other things to look at as well such as the NOAA 24h O2 exposure chart which if you are diving a high ppo2 for multiple dives will significantly come into play, also your workload can affect it as well, which is why on a hard working dive most will limit their ppo2 to 1.2ata or less
There are other things to look at as well such as the NOAA 24h O2 exposure chart which if you are diving a high ppo2 for multiple dives will significantly come into play, also your workload can affect it as well, which is why on a hard working dive most will limit their ppo2 to 1.2ata or less
Similar threads
