Trimix

[chrisch]

Out of BSAC into the fire...

The PPO2 debate revolves around the use of PPO2 @ 1.6 ATA for deco as well as IANTD's view that PPO2 of 1.5 can be used under ideal (e.g. not UK) conditions for bottom gas.  All tech diving accepts PPO2 of 1.6 exect BSAC.  Check out their forum for loads more - there are several viewpoints and no conclusions, but it does seem that BSAC are presently working hard to get technical divers to leave - shame.

Equivalent air depth relates to the relative PP of Nitrogen - i.e. PPN2 to replace the air "depth" in air tables.  For example if you use EAN32 at a WATER depth of 22m that is EAD of 17.5m.  So on a Bulhmann air table the NDL is for 18m not 22m.  The maths are easy enough as is the concept - it will not give you problems other than the expense of another (somewhat pointless) course - as you have found out.  It is not because you are not qualified for 100% O2 - the trimix course will do that for you.

There are lots of current and ex BSAC divers trying to change things.  However the more I get into the technical agency thinking the more I think this will not happen.  The wider argument of the future of BSAC is best taken up elsewhere.  However, in terms of your post I suggest you look at a basic trimix course with either TDI or IANTD.  The agency doesn't matter its really the intructor that makes the difference.  At this level we should not be "wedded" to any particular agency.

Deep air diving has had its day.  I wish you well in your trimix future!!

Best
Chris.

[Mark Chase]

Originally Posted by [b

Quote[/b] (Reeve @ Dec. 08 2003,17:31)]Is this PPO2 i.e 1.6 only applicable to the IANTD or is an approach of the TDI course as well.


gareth

Hi Garath

I did the TDI course Advanced Nitrox. They recomend a max 1.4pp02 bottom gas and 1.6ppo2 for deco. They stress the limitiations on the CNS clock as the main reasion for this. The PP02 of 1.6 only gives you 45mins in the water MAX before you violate the (theoretical) CNS clock.  So its pretty pointless. If you folow modern trends at 80% CNS you should be doing 5 air breaks as well but using a helium rich low 02 preferably for that task.

I have dived with a 1.5pp02 set for the max depth of the dive and 1.4 planned for the bulk of the dive when I know that I will only be at max depth for 15mins or less. Obviously I am trying to reduce on gassing  and reduce deco. This train of thaught is beleived wrong by some and I am hopeing to pick Bob Coopers brain on the subject on Saturday.

ATB

Mark Chase

[Reeve]

<font color='#000F22'>Howard, Daz,

Spoke to Paul today and he said that the ADV Nitrox was £250 the Deco was £250, but could be combined for £350. However he said that these and the entry level trimix could be done for £650 total for all 3. This was based on just Howard and I doing them.

It may be cheaper for more of us. At this time of year he recommended doing the course at NDC. If more of us interested then I'm sure the cost will come down but unsure of the maximum number of people he can take. If theres interest then please reply &amp; I'll try to coordinate something for us at NDC,

He did say that you'd need to have twins and a deco bottle ofr the course. I know Daz has these.

Howard he said some or all of the course could be done on w/ends but would be more difficult to arrange as his w/ends are not always free. Personally I'd rather take a week on the sick &amp; get it done. &nbsp;

Let me know your interest.

gareth

[Diving Dude]

Gareth.

l'm already Adv Nitrox &amp; deco certified, so l would only be interested in the Trimix, maybe join you for the later part of the week?

[Rupert Bear]

I am actually quite shocked that EAD is not taught on a supposedly advanced nitrox course. As far as BSAC is concerned I have always been led to believe that the enabling cert for trimix meant you dove under the trimix issuing agencies guidelines with max depth of 70m and you were covered under BSAC. I personally thought BSAC was one of the most progressive clubs as far as tech diving was concerned.
The 1.6 PPO2 argument has a few niggles that make it a bit easier than people think. Although you do have 45min max on 1.6 etc you also have to take into account the fact that you have a low PP02 for most of the dive and when you are moving up stops you may start at 1.6 on the switch but this drops as you move up unless you take about 6 stages. Generally you are on lower PP02 with spikes as you change regs unless diving with 100%.
If you work out your real loading it comes out much lower than you think unless you are doing major hangs abroad (or you don't feel the cold)

[Mark Chase]

TDI do EAD's in basic Nitrox.

The 1.4 -1.6 argument is for bottom mix we always use 1.6 for deco.

ATB

Mark Chase

[chrisch]

Originally Posted by [b

Quote[/b] (Rupert Bear @ Dec. 09 2003,09:53)]I am actually quite shocked that EAD is not taught on a supposedly advanced nitrox course. As far as BSAC is concerned I have always been led to believe that the enabling cert for trimix meant you dove under the trimix issuing agencies guidelines with max depth of 70m and you were covered under BSAC. I personally thought BSAC was one of the most progressive clubs as far as tech diving was concerned.
The 1.6 PPO2 argument has a few niggles that make it a bit easier than people think. Although you do have 45min max on 1.6 etc you also have to take into account the fact that you have a low PP02 for most of the dive and when you are moving up stops you may start at 1.6 on the switch but this drops as you move up unless you take about 6 stages. Generally you are on lower PP02 with spikes as you change regs unless diving with 100%.
If you work out your real loading it comes out much lower than you think unless you are doing major hangs abroad (or you don't feel the cold)

As ever the devil is in the detail. &nbsp;BSAC safe diving practice (SDP) states a 1.4ATA PO2 max - including deco.

Therefore you cannot deco on 1.6ATA as recommended by TDI/IANTD et al.

This has caused some people sadly to leave BSAC. &nbsp;They (BSAC) are not therefore progressive for tech divers.

EAD does not apply to the 88 tables so it isn't taught. &nbsp;I think I am correct in saying if the intructor wants s/he can teach it as an &quot;extra&quot; - something BSAC encourage and one of their better points.

You are correct that BSAC also have a 70m limit on trimix. &nbsp;This too can be a cause of disagreement.

I very much like the idea of belonging to a club with access to a RIB or hardboat and having a ready made group of buddies. &nbsp;Cheap training - especially rescue skills and first aid (something the commercial agencies don't do often enough) is a good idea too. &nbsp;There are plenty of people in BSAC that want to see the 'tech' rules changed to reflect the thinking of other agencies.

The more weight there is to this argument the more likely it is to happen.

Chris

[Reeve]

<font color='#000F22'>Chris,

Some very good points. During my Adv Nitrox BSAC course EAD wasn't mentioned it's only due to forums such as this that I have become enlightened, and further reading on the subject has provided some clarification.

Today I booked myself on a TDI adv nitrox for this w/end at NDC, to convert to TDI and hence 100%. This I guess will allow me greater scope for my deco, (subject to buddy) and if I so wish. access to the entry level trimix.

Another question for some with more knowledge. Is there an agument for (if your computer allows), for running up some serious deco while diving air, then switching to a high deco gas say 80% - 100% to reduce deco time? I would have thought it more cost effective to have a 7L of 80% than say a 15L of EAN32 times 2 and a 7L deco? Thoughts please!!!

gareth

[And]

<font color='#000080'>Hi

I would say there is never an argument to dive on air, but then I would say that

Andy

[Reeve]

<font color='#000F22'>Andy,

Sorry wasn't suggesting a deep air dive, just that bottom time on 35m+ dive, where you are on say a wreck with a square profile. Instead of diving max EAN for known depth use air &amp; then high EAN for Deco.

gareth