Max depth for Normoxic Trimix

gpion

Standart for Normoxic Rebreather class is:

- IANTD 18% o2 60m

- TDI 16% o2 60m

J.R.Gauthier

When I took my normoxic training I was taught to carry a dil that would flush @ a PO2 of 1.0 at a max depth of 200' sw (14%) and a bail out gas not to exceed 1.6 @ 200'.

Genesis

That's an interesting definition of "normoxic."

IMHO normoxic means 21% FO2. So with a 1.4 working PO2 maximum this means a depth limit of ~187'; round down to 180.

That's what - 55m?

Is 16% FO2 really safe to breathe on the surface under all exertion levels? If you've bailed and come up to 5' breaking seas staying on your reg might suddenly seem like a really good idea. Now exert yourself heavily and see what happens.

Why's the other 5m important in this case? I'm trying to get my arms around the value of "stretching" the definition of normoxic mix, given the potential for trouble.....

__________________
"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

Mike

Karl - in reality no one gives a shit.
All the normoxic ticket means is that boat drivers will let you dive on sites approximating 60m in depth.
The majority of rebreather divers will use 10/50 anyway cause it's simple and versatile - or mystery mix once they have blown a part used tank of 10/50 with air Either way it's not an issue if the rebreather is working, and you should be on seperate bailout if it's not.

Phi just wanted to know the course standards, no one much cares about the actual implementation.

Mike

__________________
Open ....... Closed
Mind ........ Loop

jhaaja

I have experience of TX10/70 on OC at 6m. Ppo2 is then around 0,16. That was not enough for me. I noticed during 1 minute that my heart rate started to rise and also breathing started to go faster. I had to change to TX20/35. I was doing a back gas break on TX10/70. The remaining breaks I did on TX20/35.

I was not swimming at all but just relaxing at a cave pool...

Dutchy

Funny that you describe a natural reaction as being not enough after one minute. Have you ever been altitude skiiing? Same ppO2 and extreme exertion. Then it's considered normal. Difference being of course that you will be wasting a lot of gas.

__________________
= This post is environmentally friendly. It is composed of 100% recycled electrons only. =

gtzavelas

Quote: (Originally Posted by Dutchy)

Have you ever been altitude skiiing? Same ppO2 and extreme exertion. Then it's considered normal. Difference being of course that you will be wasting a lot of gas.

at 7000 meters the PP02 is 0,09 (410mBar) ! And you can still do strenuous activity (i.e. climb).
The HUGE difference is that you need quite a lot of days to acclimatize and let your body adjust to the conditions. Most probably you would faint in a few minutes if you were teleported at 7000.
(in fact you would die within minutes if teleported at the summit of Everest but there are (very few) people climbing it with out O2!)

Mark Chase

Definition of Normoxic From Wikipedia:

In open-circuit scuba, two classes of trimix are commonly used: "normoxic" trimix, such as "19/30", is used in the 30 meters (100 feet) to 60 meters (200 feet) depth range and "hypoxic" trimix, such as "10/50", is used for deeper diving, as a "bottom" gas only and cannot safely be breathed at shallow depths where the ppO2 is less than 0.17 bar. In rebreathers that use trimix diluents, the mix will be "hyperoxic" in shallow water because the rebreather automatically adds oxygen to maintain a specific ppO2. See breathing gas for more information on the composition and choice of gas blends.

__________________
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]

jhaaja

No I have not been skiing high. We don`t have any high ground here in Finland unfortunately.

I guess the issue for me was that the ppO2 drop was quite large and it happened fast. Switching from O2 to TX10/70, from ppO2 1,6 to ppO2 0,16

I did not feel good so I went for TX20/35. Would not wan't to pass out at 6m with 80mins of deco left...

Janos

I once worked in Bogota, which is over 2700m high. I was fine, but one of the guys I was with had problems on the first day and passed out with altitude sickness. I felt bloody brilliant when I arrived back in the UK though (all the extra red blood cells you get when acclimatising.)

I use "Hypoxic" to describe a mix I wouldn't breathe on the surface, and normoxic to describe stuff I would.

What to people who describe everything below 21% as "hypoxic" use to distinguish between the two?

Janos

__________________
You can lead a horse to water but you can't climb a ladder with a large bell in both hands - Vic Reeves
www.hellfins.com/shed