Is my approach to diving with Nitrox logical?

[NorCalDM]

very interesting. You would think that the rates would change even if it were by a small amount. it would be interesting to see a large sample size study over many years of diving nitrox on air tables. Thanks

If you are pushing your NDL with Nitrox or Air it doesn't matter as you are still absorbing Nitrogen. You can cheat it some by running your computer in Air but you need to know your MOD for the gas your breathing.

 

[johndiver999]

The idea to use a rich mix is valid in general. The benefit (of 40% versus 32 %) for a 30-40 ft dive is probably minimal, but it probably depends on how long you are diving each day.

If I were doing one or two tanks, I would just use air and save the money. Your approach is logical, but probably not "practical". However, if I was paying a fixed fee and was going to use nitrox, I would select the richer mix.

I've dived a little past the 1.4 threshold a "few" times.

 

[Jcp2]

very interesting. You would think that the rates would change even if it were by a small amount. it would be interesting to see a large sample size study over many years of diving nitrox on air tables. Thanks

I don’t think that will be realistic because most recreational divers are using Nitrox to extend NDL time not to reduce nitrogen loading for the same NDL time as air, especially if the dive is a special travel/vacation item. This desire is even more the case with multiple multi dive days in a row, where a computer on air running a conservative algorithm might say no more diving after the second dive. Then what? I bet the diver just switched to his nitrox computer rather than skip the dive.

 

[Nitrox_DiverNY]

What benefit are you getting with nitrox over air at 40 feet. There's no point unless there's a benefit. I'll bring the mix all the way to 50% if there's a benefit.

the benefit would be the extra protection From an undeserved hit. its not common but they happen. you could still use 40% at 60 and then keep the rich as rich as the MOD allows for deeper dives. Just my way of looking at it. 40% and above is tech nitrox correct?

 

[Nitrox_DiverNY]

If you are pushing your NDL with Nitrox or Air it doesn't matter as you are still absorbing Nitrogen. You can cheat it some by running your computer in Air but you need to know your MOD for the gas your breathing.

very true, and yes running two computers would be ideal set up for this

 

[Marie13]

the benefit would be the extra protection From an undeserved hit. its not common but they happen. you could still use 40% at 60 and then keep the rich as rich as the MOD allows for deeper dives. Just my way of looking at it. 40% and above is tech nitrox correct?

Why are you so worried about DCS?

 

[DeepSeaExplorer]

Custom mixes generally require tanks to be O2 clean. Most shops bank 32%, so tanks don’t have to be O2 clean. So, there’s the additional cost there.

I used to use best mix on deeper dives for more bottom time, but at 40ft you’re not gaining anything, except a bigger gas bill the dive shop.

I’ve found myself on the boat more than once with a less than ideal mix in my tanks. Now, I keep to standard mixes.

 

[Eric802]

I've dived a little past the 1.4 threshold a "few" times.

The threshold is a moving target. I believe up until the last few years, 1.6 or 1.5 was considered "safe". 1.4 is certainly better and a safer standard.

 

[Eric802]

very true, and yes running two computers would be ideal set up for this

My .02, but running two computers that are set up differently isn't ideal for anything. Don't lie to your computer. Any computer on a conservative setting will keep you safe.

 

[Jcp2]

Let’s say that you are a very safe diver and you are worried about decompression sickness, so you want to optimize your Nitrox mix. Then I am assuming that you are also worried about running out of gas for you and your partner, so you have calculated the minimum amount of gas you and your partner will need to share off each other to get to the surface safely for the depth that you plan to dive.
Let’s say that depth is 80 feet, your calculated minimum amount of gas before ascending is 30 cubic feet at a SAC rate of 1 cubic feet/minute at the surface for each diver. You dive AL80s, each holding 77 cubic feet. This means that you should both start ascending at a gauge reading of 1200 psi. That gives you 47 cubic feet to use at 80 feet (3.4 atm). That gas will last you 14 minutes before you reach rock bottom pressure and you have to go up, well before the 25 minutes NDL on the PADI air tables and nowhere close to the 36 minutes on the 32% nitrox PADI table.

To even match the PADI air NDL limit at 80 feet, you would need to bring 115 cubic feet of air. Assuming that you aren’t each diving HP120s, the limit of you diving “safely” is not the NDL, air or nitrox, but the gas in your tank.