My AN/DP/Helitrox course

[Marie13]

I hope I'm not hijacking too much @Marie13.

Are there any studies that show an increase in likelihood to get a type 1/2 DCS hit by using TMX for DS inflation?

Yes, you are. Go start your own thread.

 

[grantctobin]

I hope I'm not hijacking too much @Marie13.

Are there any studies that show an increase in likelihood to get a type 1/2 DCS hit by using TMX for DS inflation?

I doubt you’ll find one, but there are a few including a 2005 NEDU study showing the implications of trying to offgas as your core continues to grow colder. Maybe Arthur was able to do it in 82F/28C water, but doing the same in 4C water for any prolonged duration will likely leave you hypothermic and with a much higher susceptibility to decompression sickness.

 

[rddvet]

Out of curiosity (don't think it's off topic since it's related to Helitrox/Trimix training), what were you all taught to use as a "safe" SAC rate when calculating gas required and safety margins for lost gas in your helitrox/trimix class. The reason I ask is a friend just took Trimix with an instructor who I believe to be of questionable quality and the instructor told him that he doesn't agree with the very conservative math that X, Y, and Z agency recommends because it's unrealistic to carry "that much extra gas". He had him use a significantly more aggressive SAC rate in his gas caclulations.
I was taught in both Helitrox, DPV, and CCR a conservative sac rate that was within standards set by the agency, but also in helitrox we discussed my actual sac in comparison to the more conservative sac used for gas planning. My friend seems convinced by his instructor that the less conservative sac in the calculations makes more sense because boat diving would make it more difficult to manage that much reserves. My argument that you don't want to die because you didn't want to carry gas didn't go over well.

 

[Marie13]

We’ve not been in the water yet to do SAC rate swims, but I’ve got a RMV from a cold water dive at the quarry using my Perdix AI and MacDive (which gives RMV). Mine is 0.6. That’s what we used in my dive planning class session last month. The quarry dive was 45F at 35ft, so this dive was pretty close to conditions I’d be diving on my Great Lakes wreck dives.

Of course, if my number I’d different after doing the SAC rate swims, we’ll use the new one.

 

[ChuckP]

I don't think any book needs to breathe underwater..... My SAC is .35 but jumps to .5x working, I plan .7 and dive accordingly to my consumption. I have yet to see spare bottles laying about the reef although someone lost one yesterday...........

This is warm water drift diving sidemount. My Sac warm water in steel doubles during class was .6, that could improve with time and comfort but still......

 

[rddvet]

I don't think any book needs to breathe underwater..... My SAC is .35 but jumps to .5x working, I plan .7 and dive accordingly to my consumption. I have yet to see spare bottles laying about the reef although someone lost one yesterday...........

Similar to how I was taught. A fudge factor is added into the calcualtion for safety for things that temporarily increase breathing rate. My friend was taught significantly less safety factor. To the point that the calculation is almost based off his normal sac rate. It really doesn't leave any margin for error. I assumed most people are taught similar to the way I was and obviously you were. It's scary that some are teaching very differently. And it all seems based on complacency.

 

[rjack321]

Similar to how I was taught. A fudge factor is added into the calcualtion for safety for things that temporarily increase breathing rate. My friend was taught significantly less safety factor. To the point that the calculation is almost based off his normal sac rate. It really doesn't leave any margin for error. I assumed most people are taught similar to the way I was and obviously you were. It's scary that some are teaching very differently. And it all seems based on complacency.

Same
My unstressed SAC in cold water is around 0.48-0.55
For simple math with divers I don't know very well I use a stressed consumption of 1cf/min each. For deeper dive with familiar buddies I use 0.75

I can see the merit in doing a swimming test (like in a quarry @60ft) and using that number as a stressed value. But what do you use/guesstimate for a buddy who hasn't done that?

 

[Scuba Cobra]

I have a .5 average SAC, but I plan with a .8 SAC. .45 for deco SAC.

Is your buddy being taught to plan for mingas/rock bottom? How is he planning that?

 

[Scuba Cobra]

For simple math with divers I don't know very well I use a stressed consumption of 1cf/min each. For deeper dive with familiar buddies I use 0.75

I can see the merit in doing a swimming test (like in a quarry @60ft) and using that number as a stressed value. But what do you use/guesstimate for a buddy who hasn't done that?

Same here.

 

[rob.mwpropane]

SCUBA.....the one sport where having a smaller SAC is sought after and boasted about!!!

Sorry guys (and gals)....please continue with the real conversation....I'm a child (at times)...

Edit: not directed at any one person......