Nitrox question about 1.4 and 1.6

Tatakai · Jul 27, 2006

I finished up my class training the other day and I am going to do the dives next weekend. Going through the class my DM said that we use the 1.4 as our MOD and 1.6 is our COD. I understand that and can agree to the safety margin of using the 1.4. This is a PADI course as you might have guessed. So to get to my question which one do you use and why? Is it more of the way some others do the training or is it just a safety margin that PADI has adopted for training?
Thanks everyone for all the info that I have received from this site. I have to get on here a few times a day to see what I have missed and to read topics of interest to learn more.

Tatakai

Red Vette · Jul 27, 2006

I try to stay at 1.4 (lower on my Drager) as we all react to partial pressure differently. I have on rare dives gone to 1.6 but I don't like to test the limits. Have fun!

lamont · Jul 27, 2006

the more that i dive, the more i'm leaning towards a 1.2 max pp02 rather than 1.4

Bobby · Jul 27, 2006

My max PO2 for the working part of a dive is 1.4 hard and fast. If I am doing new exploration I will drop my PO2 down to 1.2 For deco I push the PO2 up to 1.6 If you are doing recreational dives (you are at the momment) plan your dives with a max PO2 of 1.4 and do not go over it.

The reason for this is that the amount of energy you use on the dive will directly affect a possible CNS hit. If you push over 1.4 on your PO2 you are setting yourself up for disaster. Years ago when we were just starting to work with O2 & Nitrox some decided to push the PO2 limits and most of them paid the price with their lives. This is not a PADI standard it is a diving industry standard that has been proven time and time again. Good question and I am glad you asked before making a decision on your own to push the PO2 limits.

Bobby

havnmonkey · Jul 27, 2006

I think the difference in recommendations is that a lesser % of people are susceptible to O2 toxicty at 1.4 and a higher % of people are susceptible to O2 toxicity at 1.6. I think it also has to do with the stress on the diver induced by the dive and conditions; a deep dive in cold water with low viz and a ripping current might make you more prone to everything: Nit. Narcosis, DCS, O2 TOX, etc.

Jake · Jul 27, 2006

I'm actually surprised that the RDPs use 1.6 as a contingency limit. Based on my reading (in particular, Brett Gilliam) and experience, you're asking for a lot of trouble by heading to that limit, even when it's a contingency. As others have said already, I would consider making 1.2 your MOD and 1.4 as your COD. Make sure your friend has this plan as well, and you should both be safe. If for some reason, you decide in the future that you need to push the MOD/COD, you might want to consider getting a full face mask. At the very least, that will *help* prevent drowning should you start convulsing. I would absolutely not recommend you tempt fate though.

Meng_Tze · Jul 27, 2006

Bobby F:
My max PO2 for the working part of a dive is 1.4 hard and fast. If I am doing new exploration I will drop my PO2 down to 1.2 For deco I push the PO2 up to 1.6 If you are doing recreational dives (you are at the momment) plan your dives with a max PO2 of 1.4 and do not go over it.

Bobby

What he said

redacted · Jul 27, 2006

I use the 1.6 limit but rarely exceed 1.4. Recreational dives with low workload and very short times over 1.2. If I had the option of 28 to 30% for those dive, I'd probably take it.

--tom-- · Jul 27, 2006

Because of the depths and times I dive, I rarely exceed 1.4. I thought running the ox tox gradient and the DCS gradient was quiet meaningful at 1.4.

redacted · Jul 27, 2006

Bobby F:
Years ago when we were just starting to work with O2 & Nitrox some decided to push the PO2 limits and most of them paid the price with their lives. This is not a PADI standard it is a diving industry standard that has been proven time and time again. Good question and I am glad you asked before making a decision on your own to push the PO2 limits.

Bobby

What do you mean when you say some pushed the limits and most paid with there lives? Are you talking PPO2 in excess of 2.0? 1.8? It is my understanding that there is an increased risk as you push from 1.4 to 1.6 under certain conditions including higher work loads and extended times (more than 5 minutes). Otherwise, the incidences of CNS in that range are extremely low.

Nitrox question about 1.4 and 1.6

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Tatakai

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