why a 32 mix standard?

[cmalinowski]

Hi,

I have no problem with using Hyperoxic gas for the deco. But why TMx? It is much more expensive and we do not need TMx for 36 m.s... Do we? Why not EAN35 instead of TMx 35/25

What I was telling here was if we use Trimix 35/25 at depth 36 m. then we will have an END of 13.5 m.

Why do we need a gas which gives us END=13.5.

I'm OK with high O2 percentage, which helps for shorter deco durations.

Regards,
Yener

Still not getting where your 13.5m is coming from for END. My END calc comes up with 24.5m or the GUE recommended 80' END (100' being max). So, considering that GUE recommends 1.6ppO2 max and END of 80', then the mix starting at 36m nails that on the head. My guess is that's why they use it.

In addition to Soggy's great points: Getting rid of the helium will also increase the WOB due to the viscocity of the gas (O2/N2) thus building up CO2 which is bad. CO2 is narcotic at a minimum, and the whole process could lead to a build up of lactic acid/catacolomines and some people believe that may have an impact on OxTox. At 1.6ppO2, I just don't see the need for that gamble... especially at 36m with a pretty hefty deco obligation left.

So, there are some reasons for that particular mix from my perspective. Expense doesn't play into it. If you're doing a dive that requires this gas, you're splitting hairs from a price perspective as the rest of the dive probably costs a good bit anyway.

Hope this helps.

Chris

 

[Soggy]

Still not getting where your 13.5m is coming from for END. My END calc comes up with 24.5m or the GUE recommended 80' END (100' being max). So, considering that GUE recommends 1.6ppO2 max and END of 80', then the mix starting at 36m nails that on the head. My guess is that's why they use it.

Yeah, the END on 35/25 at 120fsw is 82 fsw or 25 meters according to V-planner. My quick math came up with 77 fsw, so I'm not sure where the discrepancy is.

 

[lamont]

I have no problem with using Hyperoxic gas for the deco. But why TMx? It is much more expensive and we do not need TMx for 36 m.s... Do we? Why not EAN35 instead of TMx 35/25

if i ever find myself using a 120 deco gas bottle the extra $10-$20 for the 35/25 will be negligible and i don't need to be narc'd at 120 with that much deco obligation over my head. you can cut your safety margins as tight as you want to though to save a couple bucks...

 

[edparris]

Still not getting where your 13.5m is coming from for END.

He's assuming only the nitrogen is narcotic:
END = [(FN2 * (Depth + 10))/ 0.79 ] - 10

 

[MonkSeal]

Yeah, the END on 35/25 at 120fsw is 82 fsw or 25 meters according to V-planner. My quick math came up with 77 fsw, so I'm not sure where the discrepancy is.

Assuming 120 fsw = 36 msw, metric calculation gives END = 24.5 m. That's roughly 82 fsw or 25 msw.

 

[cmalinowski]

He's assuming only the nitrogen is narcotic:
END = [(FN2 * (Depth + 10))/ 0.79 ] - 10

Yea, I know. I was just hoping to get them to actually say it

Maybe it was just a troll... Must be something in the air. Everyone seems to want an argument lately. Even I am not immune :mooner:

 

[Soggy]

Assuming 120 fsw = 36 msw, metric calculation gives END = 24.5 m. That's roughly 82 fsw or 25 msw.

[.4PN2*(4.63ATA)] / .79 * 33 = 77 fsw

According to google, 120 ft is 36.57 meters.

I don't do END calculations manually all that often, so I could have messed the above up.

 

[MonkSeal]

[.4PN2*(4.63ATA)] / .79 * 33 = 77 fsw

According to google, 120 ft is 36.57 meters.

I don't do END calculations manually all that often, so I could have messed the above up.

We assume O2 is narcotic - different formula should be used.

 

[Soggy]

We assume O2 is narcotic - different formula should be used.

I think I just had a brain fart....thanks.

Actually, my math and/or formula was just completely wrong...

This is what I meant
(0.75 *((120/33)-1)/0.79)*33 = 82 ft or 25 meters

.75 is the PNarcotic (PN2 + PO2, or 1-PHe)

 

[MonkSeal]

Here's the article describing different approaches in END calculation: http://techdiver.ws/trimix_narcosis.shtml