Alternate Gas Backup Computer

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arew+4

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So my wife and I are going to start diving nitrox on air settings, plan to continue using our pro plus 3s as primaries in air mode. I want to run back up computers in nitrox mode at for actual gas values to track O2 exposure, and MOD etc.

Question is how important would it be to match deco algorithms?

TIA,
 
You'll never reach a high-enough O2 exposure to worry about it.
MOD is just one depth to note on each dive. Not a big deal.

Why not run your primary computer on Nitrox, and just stay away from NDL?

A backup computer is a good idea, and matching deco algorithms is nice if you have both computers set the same, but trying to game the system like you are doing kind of means the algorithm isn't that important.
 
So my wife and I are going to start diving nitrox on air settings, plan to continue using our pro plus 3s as primaries in air mode. I want to run back up computers in nitrox mode at for actual gas values to track O2 exposure, and MOD etc.

Question is how important would it be to match deco algorithms?
Not important at all. The computer tracking on air will run out of NDL before the other computer in most situations. In any situation, they won’t match.

I’ve got to ask why. If you want the extra safety buffer, but also want to track O2, just run it in the mix you are breathing but use the most conservative setting, or just run it in the usual conservatism and ascend when NDL gets down to X minutes.
 
Nitrox on air is just a brain light, no pushing it sort of thing. You can always find a reason to justify staying just a few more minutes if there is time on the clock. This way there is no time on the clock, even if there is some in the bank.

The back up is just there so in the event something were to occur there would be an accurate record. Figured the algorithms did not need to match but wasn't sure if some of the models could be incompatible. Buhlman vs bubbles etc.
 
Nitrox on air is just a brain light, no pushing it sort of thing. You can always find a reason to justify staying just a few more minutes if there is time on the clock. This way there is no time on the clock, even if there is some in the bank.

The back up is just there so in the event something were to occur there would be an accurate record. Figured the algorithms did not need to match but wasn't sure if some of the models could be incompatible. Buhlman vs bubbles etc.
Well, you've clearly already decided what you are going to do, whether it makes sense or not.

You can't match algorithms, not if one computer is on air and the other is not.
You can use the same algorithm, but you can't match them.
And there is no reason to use the same algorithm.
 
Man, I feel a Slim Pickens quote coming on.

Or Festus would be a good option, too.
 
Nitrox on air is just a brain light, no pushing it sort of thing. You can always find a reason to justify staying just a few more minutes if there is time on the clock. This way there is no time on the clock, even if there is some in the bank.

The back up is just there so in the event something were to occur there would be an accurate record. Figured the algorithms did not need to match but wasn't sure if some of the models could be incompatible. Buhlman vs bubbles etc.
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Nitrox on air is just a brain light, no pushing it sort of thing. You can always find a reason to justify staying just a few more minutes if there is time on the clock. This way there is no time on the clock, even if there is some in the bank.

The back up is just there so in the event something were to occur there would be an accurate record. Figured the algorithms did not need to match but wasn't sure if some of the models could be incompatible. Buhlman vs bubbles etc.
The extra risk you run is that you over run, get into deco and get low on gas doing ”deco” when in fact well within your NDL. (I have had to donate gas to a person in this position.) Having the second computer which you are not lying too is better but then what is the point of the first computer?

The best way to do this is to use something like a shearwater on a conservative setting but be prepared to use the GF99 or SurfGF indicator to surface early if required. Eg, dive 30/70 but be prepared to surface with a GF of 85. Many people here say the opposite, dive 45/95 but only surface with a GF of 70 but that has disadvantages regarding how realistic the NDL is and amounts to a deco dive with deco you might decide to skip.
 
https://www.shearwater.com/products/peregrine/

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