rec trimix deco tables

[lamont]

35% is helium, the nitrogen is omitted.

 

[wedivebc]

Webdive, you posted your thread in Basic Scuba Discussions. As a result, I assumed it is was a "Basic" question.

recreational trimix is basic scuba.

 

[Soggy]

Soggy, thanks for the response.

You say 21/35. What is the other 44%? Is that the helium?

21/35 is 21% O2, 35% He, 44% N2

 

[Nomad]

21/35 is 21% O2, 35% He, 44% N2

Thanks for taking the time to share your knowledge.

 

[gstroupe]

I can't tell from the pics, you know what algorithm they use?

Says the following on the site: "These tables are all based on the Varying Permeability Model B (VPM-B) algorithm."

they are published by IANTD.

 

[WaterDawg]

I think you guys forgot what you were arguing about.

 

[ianr33]

...and I didn't throw any sarcastic insults.

Anyhow, because helium is both faster ongassing and offgassing, unless you are breathing extremely high helium mixes or doing extremely long dives, you can more or less ignore the helium component as long as you keep your ascent nice and slow.

For a recreational dive on 21/35 (over kill, but happens when we get blown out of a deeper dive), I dive like I'm using air, but just do 1 minute stops from half maximum depth rather than a single 5 minute safety stop.

So why does anybody buy a trimix computer?

 

[PerroneFord]

So why does anybody buy a trimix computer?

For the same reason recreational divers use air/nitrox computers.

 

[ianr33]

I think you missed my point

If you play around with V-Planner looking at profiles down to 200 feet for 30 minutes and using around 35% He the run times on air are only 3 or 4 minutes longer. So if you are not doing anything really extreme why not use an air computer (as a backup to your tables of course!!) and use something like a DiveRite Duo rather than a VR3 and save yourself a $1000 (assuming you only use one deco gas ,are not diving CCR etc etc)

 

[artek]

Some pp buy trimix computers, some use calculators or software others use abacus and some of us just know what the hell we do down there , ain't golf course.:smoochie: