Rebreather World - View Single Post - Gradient Factors

Mark Chase · 2nd May 2008, 19:51

Quote: (Originally Posted by athomson)

I've a question for anyone out there who can give me staright answer.

I've been diving rebreathers for over a year and have just completed my Mod 2 in Malin Head. Yes, April in the North Atlantic and it was f$&%*ing freezing! Great course but may not have been the best time of year for it.

Anyway, I'm still trying to get a better understanding of gradient factors at the moment with regard to air dil and trimix dil. Until recently, I dived the Vision Nitrox Software with a conversatism setting of 3, which is 90/90, so fairly close to Bulhmans. With the trimix software now installed, I've started diving with 20/80 GF set. I'm still jumping back and forth a bit between the trimix and air dil depending on the dive. However, I have noticed that if I do an air dil dive with 20/80, I feel crappy after the dive (aches, pains, and generally cream-crackered) while I feel generally fine after a trimix dive. Now, I've started diving the 90/90 for air again .. no problems.

What I'm trying to understand is why this is. I would think that the 20/80 is more conservative and hence better for me. I've also sent this question by email to my Mod 2 instructor so if I get an answer from there, I'll post it.

Any comments or ideas would be welcome.

Regards,

Andy T

In the very broadest of terms....

Trimix uses Helium and Helium deco benefits from deeper stops so its better to do more deep stops on trimix than on air.

Empirical data? I have never seen any one in the water bent on Nitrogen but I have witnessed divers bent on the 6m stop due to helium.

So an aggressive trimix deco for me is 30/120GF but and aggressive Air deco is 100/100

As for you're diving... try going pure 02 for the last 20mins of ANY deco. It worked wonders for me.

ATB

Mark

2nd May 2008, 19:51	#4 (permalink)
Mark Chase RBW Member Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,817	Re: Gradient Factors - Air Dil vs Trimix Dil Quote: (Originally Posted by athomson) I've a question for anyone out there who can give me staright answer. I've been diving rebreathers for over a year and have just completed my Mod 2 in Malin Head. Yes, April in the North Atlantic and it was f$&%*ing freezing! Great course but may not have been the best time of year for it. Anyway, I'm still trying to get a better understanding of gradient factors at the moment with regard to air dil and trimix dil. Until recently, I dived the Vision Nitrox Software with a conversatism setting of 3, which is 90/90, so fairly close to Bulhmans. With the trimix software now installed, I've started diving with 20/80 GF set. I'm still jumping back and forth a bit between the trimix and air dil depending on the dive. However, I have noticed that if I do an air dil dive with 20/80, I feel crappy after the dive (aches, pains, and generally cream-crackered) while I feel generally fine after a trimix dive. Now, I've started diving the 90/90 for air again .. no problems. What I'm trying to understand is why this is. I would think that the 20/80 is more conservative and hence better for me. I've also sent this question by email to my Mod 2 instructor so if I get an answer from there, I'll post it. Any comments or ideas would be welcome. Regards, Andy T In the very broadest of terms.... Trimix uses Helium and Helium deco benefits from deeper stops so its better to do more deep stops on trimix than on air. Empirical data? I have never seen any one in the water bent on Nitrogen but I have witnessed divers bent on the 6m stop due to helium. So an aggressive trimix deco for me is 30/120GF but and aggressive Air deco is 100/100 As for you're diving... try going pure 02 for the last 20mins of ANY deco. It worked wonders for me. ATB Mark __________________ See my "Doing It Chasey" video where I'm locked into a padded room, naked, with two ball bearings and within an Hour, I manage to lose one and break the other!!! Kevin Juergensen 16/11/08 [/quote]
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