Which do you think is less dangerous at 160ft? Open-circuit air or CCR trimix?

[gschaut]

If you have trimix available (and certified), OC trimix is your best bet. for 160' you can use 20/30 trimix and have aprox the same END as 100' on air. Of course, you must be certified in deco, 100% O2 deco mix and normoxic trimix..

 

[lermontov]

This is very interesting. Out of a sample of 80 divers pressurised to 190 Ft on air, about 20% had no problems with puzzles or problems. While it may be argued that the sample may not be big enough, it does provide some evidence that some divers can operate deep on air. I wonder if any research has been done to explore this phenomenon.

Similar phenomena exist with decompression shedule, oxygen tolerance, hypothermia

$15K plus the cost of a basic course (about 5 days) buys you no deco dives to 40 metres. No advantage over OC air.

If you want to buy deep dives on tri mix requiring deco, it's going to take more courses and a few years to achieve. It will probably cost about $50K+.

Don't forget annual servicing costs and periodic refurbishment costs. Also, if you want to be safe, you need to dive the rebreather regularly. It is a complex beast with lots of potential failure points.

If you have the money, and believe you have the right attitude for rebreather diving. Go for it.

ive never met a ccr diver yet that has brought one to save money - generally they buy them because its the right tool for the diving they are doing and theyre awesome in terms of iberating you from some OC diving parameters

ccr diving is intensive both in and out of the water

if your worried about the cost of your diving hobby - technical diving is not for you or is beyond your means

 

[Wibble]

Memories of an “air” dive (actually 25% following a top-up on 32%) down to 50m/165ft.

I was utterly off my tits with Narcosis. Constantly checking my gas pressure and depth, incapable of any logical thought and would have been exceedingly difficult to do fault-finding.

On a 45m/150ft sea dive on nitrox I was talking to the fish. What next, do you want to breathe some of my gas?

Being narked off your head isn’t fun. Neither is drinking two bottles of wine and driving home.

Sorry mate: trimix is the answer. CCR makes deep diving—way beyond those shallow depths mentioned—possible and safe.

 

[AJ]

This is very interesting. Out of a sample of 80 divers pressurised to 190 Ft on air, about 20% had no problems with puzzles or problems. While it may be argued that the sample may not be big enough, it does provide some evidence that some divers can operate deep on air. I wonder if any research has been done to explore this phenomenon.

Similar phenomena exist with decompression shedule, oxygen tolerance, hypothermia

$15K plus the cost of a basic course (about 5 days) buys you no deco dives to 40 metres. No advantage over OC air.

If you want to buy deep dives on tri mix requiring deco, it's going to take more courses and a few years to achieve. It will probably cost about $50K+.

Don't forget annual servicing costs and periodic refurbishment costs. Also, if you want to be safe, you need to dive the rebreather regularly. It is a complex beast with lots of potential failure points.

If you have the money, and believe you have the right attitude for rebreather diving. Go for it.

I get severly narced beyond 30 meter's on air, so for me a ccr with trimix is a no brainer wanting to dive deep wrecks. Besides that, I like the added 'gas time' and warm breathing gas when doing cold cave/mine dives. It makes me uneasy to have aa fairly limited amount of cold gas in those circumstances. So for me a ccr was the way to go not mather the cost.

I consider it a safety enhancement instead of a liability.

 

[lostsheep]

To lost sheep,
Your two dives to 45m. Where they on air diluent or trimix diluent? Either way you can do 45m on air OC. Ref. TDI Decompression Procedures Course - entry level course for technical diving.

To nadwindy,
I agree. If you fall in the 80% group you are definitely taking a risk on deep air. You definitely should be following current established rules.

Can and should are not synonyms.

Deeper class dives were on helitrox.

 

[AeroSpartacus]

$200 x 50 dives =$10,000
50 dives is not that many.

In the context of CCR, it wouldn't be $200 per dive though. I filled up a set of 85s with 30/30 and used it for 4 long days of diving recently (it would have lasted longer, but I was taking a crossover class so it included some bailing out to open circuit and SCR drills). Especially if you're running your dry suit / BC off a separate bottle, the diluent can last a *long* time.

Edit: Ah I see you were arguing in favor of using a rebreather over OC, I misread

 

[broncobowsher]

It provides evidence that 80% of divers have problems. That's a pretty effing large percentage that are going to be messed up on air at that depth. Thanks for adding to the proof that deep air is stupid.

From the sounds of it, it was a single test. If you have ever been narced, you will realize it isn't 100% repeatable. You might do 10 identical dives and only get narced on one of them. Or you get narced on all 10 of them. Just because you drove home from the bar drunk one night does not mean you can do it every night.

 

[CG43]

This is very interesting. Out of a sample of 80 divers pressurised to 190 Ft on air, about 20% had no problems with puzzles or problems. While it may be argued that the sample may not be big enough, it does provide some evidence that some divers can operate deep on air. I wonder if any research has been done to explore this phenomenon.

" I wonder if any resarche has been done to explore this phenomenon . "

May be some resarch exist , but is it widely used ? I don't think so .
It is easier to reduce the maximum depth than to train divers to dive slightly deeper on air.
The disadvantage of this lack of training is that problems and completely unnecessary accidents can occur even in moderate depth .
Shallow depth limit or deep air training , both has its safety advantages and disadvantages .

To nadwindy,
I agree. If you fall in the 80% group you are definitely taking a risk on deep air. You definitely should be following current established rules.

With the right training, it is not necessary to stay in this 80% group.
If you are interested in you can read about .
For exable : Hall Watts and Bret Gillings and what Angelo Farina writes about Raimondo Bucher .
This is not a real science but there are interesting similarities that can be compared and tried out .

scubaboard.com/community/threads/adding-helium-some-numbers-to-think-about-narcosis.586769/

 

[old frogman]

You do mod1, some practice dive (20? 50? If you really want to stretch, 100h, which is doable in one/two years but will definitely cost less than 5k for most people including extra expenses like driving etc. At least here in Europe), then Mod2. If you have previous tech experience maybe you can even go faster.

INCLUDING FUN DIVES we are definitely below 20k for most divers.

Btw, this wasn't the point of @ofg-1 at all - his point was, if for once you have to go for trimix, just go, it won't change much overall.

Hi Ginti,

Thank you for your input. I agree that if you stretch things, you may be able to achieve Mod 2 level in under $20K which should enable you to dive to 60m on trimix. If you want to stretch things, I have no problem with that.

Whatever decision you make, CCR or OC, air or trimix. It is essentially a matter of individual capability, confidence, perception of risk and tolerance of risk.

To quote Winston Churchill, a man who knew more about risk than most.

"Rules were made for fools to follow and wise men to be guided".