Increasing no-deco time

[MJillKDives]

I'm using a rather conservative Cressi Sub Archimede. On easy- going, warm water decompression dives I would like a little less hang time. (I recently dived in Palm Beach with two others, one using an Aeris and the other a US Diver's Monitor 2. We dived the same profile. When they were ready to surface, I still had a 5 minute decompression obligation.)

Here's my question: Can I tweak a little more no-deco time out of the computer by setting it for altitude rather than sea level?

[Atticus]

I do most of my diving in Tahoe which is at 6229' elevation.

First let me say that I'm not wild about the idea of trying to trick the computer into giving you more bottom time / shorter decos. If there are risk settings / personal settings you may be able to use them to get in sync with your buddies. Anything other than that is probably a mistake.

To answer you question directly - if you tell your computer it is at altitude it will assume you are surfacing to a lower pressure. This means that you will need to deco longer, not shorter prior to surfacing. We teach open water students to use an altitude correction chart - a dive to 40' in Tahoe is calculated as a dive to 50' due to the altitude.

The best suggestion I can give is to follow the most conservative computer. It will make everyone that much safer.

Also, if you're doing deco diving, you might consider cutting tables for the dives in addition to using the computers. This could resolve the different profiles problem that you're having now.

[Charlie99]

MJillKDives once bubbled...
I recently dived in Palm Beach with two others, one using an Aeris and the other a US Diver's Monitor 2. We dived the same profile. When they were ready to surface, I still had a 5 minute decompression obligation.

As Atticus noted, setting to altitude will decrease NDL.

Long drift dives at 60-90' on SE Florida's 3rd reef are the ideal dives for Nitrox.

[MJillKDives]

Nitrox! Why didn't I think of that? (I'm even certified!)

Thanks, its much better advice than trying to fool the computer.

[pdoege]

With Nitrox I can stay down longer than the boats will let me. The Archimede is more conservative than the SSI tables.

I've been thinking of picking up a Dive Rite Plus. It is actually designed to support deco and allows 1 gas for switching.

Peter

[Walter]

"Can I tweak a little more no-deco time out of the computer by setting it for altitude rather than sea level?"

No, but that will get you less bottom time.

[MikeFerrara]

I hate to say it but it doesn't sound like you know much about decompression.

Optimizing decompression isn't about tweaking settings on a computer, it's about developing a decompression strategy that fits your needs that you're comfortable with. That might mean less decompression or it might mean more.

If you're using that computer for decompression I'd assume your doing deco on back gas. That's the first thing you should probably change, IMO.

[ScubaRon]

If you want less "hang time" and thus increase the risk of DCS, why not just skip the last 5 minutes? Tweaking your computer, even if it could be done, would only give you a false sense of safety.

The other thing you need to be aware of is that computer profiles behave differently for multiple-dives. Your computer may be 5 min's more conservative on the 1 st dive, but may give you more time on the next one.

My recommendation: don't tweak your computer.
ScubaRon