Agency choice and helium in 1st CCR class

Steve

Gee I don't know. What ever happened to the old addage; do 20 dives before diving deeper than 20m, 30 before going past 30m and 40 before going past 40m? On changing from OC to Rebreather I basicly took a year off from trimix so I could set a solid foundation of well practiced skills.

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edster

Bang on!

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schford

Gets my vote.....

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JPJones

Some people don't dive with and END below 80 ft and there is no reason that they should have to for a course. Your right though the basic course is based around survival not diving deep or gas diving that comes later.

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lizardland

I dive trimix diluent pretty much all the time for a number of reasons. Primarily, I get a 12l filled with rich trimix and a pair of 300bar 7's with air every now and then and decant it into my dil bottle and do air top offs. It saves the hhassle of getting to dive shops as my local doesn't open late. I'm not going to dump my leftover dil just so I can get a pure air fill for shallower diving. I also like how it makes me feel post dive on shallower dives as opposed to an air dil. It is noticeably easier to breathe as well which must be a good thing.

I kind of did the opposite, I gave up OC trimix diving in the run up to getting a KISS and started using helium dil on (I think) my third or fourth dive. In progressing deeper I found the major source of stress at depth was bailing out back to OC rather than diving the rebreather.

The way I've approached my own diving and choice of diluent is that if the dive wouldn't benefit from use of helium then it probably doesn't benefit from using a rebreather either and I go back to OC.

And Steve, your avatars must be the best on Rebreather World.

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Nick uk.

This is a good point of view, wich i think gets overlooked!

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edster

True enough - but then there is the question of how deep you get taken on the course. I mean, we're talking about learning to dive a box here - MOD1 or equivalent. An END of 80ft is about 25m in metric, which at an SP of 1.3 is about 31m.

Instructors help me out here, would you be taking students past 31m (abt 95ft) on their first course? I didnt go that deep, and not sure that I know anyone who did.

cheers

Ed

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Mdemon

I was taken to the limit, as were most people I know. I think there is a requirement to get within a reasonable distance of the cert depth by some agencies.

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"Once the agenda-monkeys and perfect-worlders have moved on, perhaps we can do some diving?"

Mark Chase

I wouldn't advise anyone use Helium as their diluent until they get control over buoyancy. A rapid ascent on Helium is going to do a lot more damage than a rapid ascent on just plain old air. Buoyancy on a CCR is a PITA.

The problem is when you get past the 20 dives to 20m bit.

100 hours over a minimum 100 dives is the problem. Once you have a lid on buoyancy control then I would be venturing deeper than 25m and my personal narcotic limit is 25m. I just refuse to spend 100 hours shallower than 25m because there just arnt that many decent shallow dives out of Brighton the vast majority are in the 30 zone and that to me means Trimix.

If they said 20 hours max depth 20m then allowed Trimix it would be a much better system.


TDI is out of date and out of touch with modern diving practice. There is no need to suffer narcosis it does nothing to enhance your diving so why put up with it.

People who say there fine on air at 30m are like people who say drinking three pints doesn't affect their ability to drive. All the evidence is stacked against them. The fact that they can function does not detract from the fact they are defiantly suffering a reduction in cognitive ability and reaction time. Its a fact and thats that.

In my case I am pissed as a fart on three pints and have on occasion been seriously impaired at 30m in UK conditions.

In clear blue warm water ill happily dive to 40-50m on air dill. On one occasion i dropped to 63m on air and shot reasonable video of the dive. Only difference is i am fully honest about the fact if it all became suddenly a bit stressful id be in a lot of trouble.

In the UK diving wrecks in low viz covered in nets snags and accidental entry points its always a bit stressful so I use mix.

ATB

Mark Chase


Mark Chase

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Joe

It has been my experience (OC - still a greenhorn on CCR) that He gives a cleaner, easier decompression and in 20 - 30 % range can be dived the same as air.

I see no reason why one should dive what he believes to be an inferior mix simply because he is taking a course & I doubt any instructor would object to He so long as the FO2 was appropriate for the course.

That said, while there is nothing wrong with using air for shallow dives, IMO, after a *long* day of diving, even shallow, the difference in how you feel afterwards with He vs air is quite noticeable and that alone is sufficient reason to want the He.

Personally, I dive whatever I have and as far as the He goes, more is better. I only concern myself with the O2 % since that is the one that will kill you.