Agency choice and helium in 1st CCR class

ameirowi

I am a rebreather novice and rebreather world newbie with classic Kiss on order-

I have a fair amount of OC trimix experience and training, and noticed that IANTD's first Kiss class allows use of normoxic mix for dil and the TDI standards don't seem to allow this (I have gone through the TDI manual and it doesn't speak to this point at all). My newbie view is that I will want a fair amount of experience between mod 1 and a mix ccr class but that using normoxic mixes as a dil for dives in the 100-150 ranges while getting the experience and having fun makes a lot of sense. If this is correct the TDI standards seem suboptimal.

Any reactions/corrections to this.

Thanks
A

Genesis

IMHO as a gasbag novice as well but with significant deep-diving experience, you're simply nuts NOT to dive with normoxic Trimix originally on a Rebreather.

The ONLY argument for not using Trimix below 80-100' is, in fact, an analysis that has a cost component in it.

With a Rebreather that issue disappears as the cost differential is now literally a buck or two at most.

I believe you've got it right, but that you are being quite kind about using the phrase "sub-optimal"......

__________________
"A venturesome minority will always be eager to get off on their own, and no obstacles should be placed in their path; let them take risks for Godsake, let them get lost, sunburnt, stranded, drowned, eaten by bears, buried alive under avalanches - that is the right and privilege of any free American."
http://www.denninger.net
http://www.diversunion.org/liability.htm - Fix the Diving Cert racket

mikedive

Hello guys,

Just remember; the IANTD standard say:
"You can do the CCR MOD 1 course using He mixes but based on the Adv. Recreational Trimix diver standards and it limit you to a maximum depth of 150ft/45m and a minimum of 28% of O2 on the mix".
Cheers,

Mike - www.protecdiving.com

Genesis

150' on 28%? You be brave my friend; that's beyond the O2% I'd run at that depth.....

__________________
"A venturesome minority will always be eager to get off on their own, and no obstacles should be placed in their path; let them take risks for Godsake, let them get lost, sunburnt, stranded, drowned, eaten by bears, buried alive under avalanches - that is the right and privilege of any free American."
http://www.denninger.net
http://www.diversunion.org/liability.htm - Fix the Diving Cert racket

JPJones

You can use 21/15 or 21/30 the 28% doesn't apply to CCR and the depth limit is now 160ft. The 1.0 max dilent po2 at deepest depth over rides the 28%.

__________________
NSS/CDS Training Chairman
www.jpjscuba.com

Underwaterbear

My guess is that it says 28% to allow for FiO2 drop when doing SCR drills at the surface during the class. Ok, fair enough for the class...albeit a tad unrealistic.

In the real world, if you were under my supervision I would support you diving normoxic mix within the limits of your MOD1 cert and your personal limitations.

Under your own cognizance, do whatever you want. I do. The net-nannies haven't got to me yet.

ameirowi

Thanks for the clarrificaiton on IANTD. 21/15 or 21/30 seem like fine choices. Does anyone here have experience with this being allowed in TDI mod 1 courses?

__________________
I have millions of closed circuit dives --they were all very short and seperated by open circuit inhalations and exhalations

Rich Sawkins

I think you'll find it's a complete NO NO ....

http://www.tdisdi.com.au/tdi_course.php

When I did mine is was specifically AIR dil, 40M max.

nigelh

Mod 1 is a non-deco course based on learing to use the rebreather.
Do it on air. You don't need to go deep enough to care about 'mix.
You are doing lots of ways a rebreather can fail and how to survive them.
I never went below 20m but spending 45 minutes at a time driving the thing manually and getting flash-carded with faults was hard work.
Get the knowledge. Shake hands.
Go home and put mix in it.
Go dive and relearn buoyancy so it just works again.

I dived 'mix before I did the next level course because I nark badly.

__________________
nigelh

schford

Playing Devils advocate why are you nuts?

I don't dive with Trimix all the time on a Rebreather, neither does Leon, Bruce, Ron, Sarah, Stefan - I could go on....

There are advantages and disadvantages - In blue water fluffy diving abroad I really dont have a problem diving on air as a DIL. To be honest for fluffy dives in this country I am not overly concerned either.

The pluses are it can and does give you a clearer head when you get over 100 foot, sub 100 foot I realy dont notice a jot of difference and to be honest in blue water it is really only 130 plus foot that I would consider it

The negatives are, it is addtional cost in both time and cash in preparing for a dive, it can complicate your decompression and He can be hard to lay your hands on.

It could also complicate things if you have a repid ascent as a learner.

Plus if some one had not dived trimix before why complicate things with additional forumlae and theory to learn etc.

My biggest fear though is that iwith He in the mix it WILL tempt new divers into going deeper then they would on air when they do not have the hours yet on the unit to be ready for it.

Stuart

__________________
Bailout and Kit Management account for Murphy's Law

The only bad question is one you did not ask and later wish you had.

Use of Rebreather World is subject to the Rebreather World Terms & Conditions of Use