O2 for suit inflation on deep Rebreather cave dives

Barrie Law

I have often dived using O2 to drive my DS although not in caves.

The Molecular size of Oxygen makes it an ideal candidate for suit inflation and due to it's large size (relatively) it has good insulation properties.

The Oxygen supply cylinder used for suit inflation would be an 'off-board' fitted with a low pressure whip that would also fit the manual inject button on my CCR if the need arises.

Like DRMike if there is a proven instance of diver injury due to using O2 in the DS I would like to hear about it, none exist outside of the 'pub rumour' to my knowledge.

Risk assessment and dive planning aside using O2 in your DS is probably something you do not need to be worrying about during your dive but I would not castigate those who do choose to use it accept maybe the smokers amongst us.

Regards

UKSteve

Mike,

At risk of sounding daft (nothing new there!!) how about using the same method that UK navy divers used to use...with a small bottle (a la ABLJ bottle still available from AP Valves) plumbed in directly to the suit? Would be minimum profile. Used only to take off the squeeze at depth - having used other gases on way in?

Steve

Mdemon

Well, I've watched Ray Mears rub two sticks together for 30 mins and he still found it tough to get a fire going by friction...

My point through my posts is that you need to ignite something for the O2 to make any difference. So, unless your match/cigarette/spark touches something combustable, nothing is going to go up in flames other than the things already burning. You could put your cigarette inside your O2-filled DS - just don't drop it!!!

In the spirit of experimentation, I have made the following; please note, no divers or camels were hurt in the making of this movie.

www.southwestmafia.com/burnbabyburn.wmv

__________________
www.southwestmafia.com

"small minds talk about people, Average Minds Talk About Events, GREAT MINDS TALK ABOUT IDEAS!"

The WRONG Attitude will get you killed.

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

Barrie Law

Classic.

Sutty

I agree that you need an ignition source and this may not be likely, I'm just not confident its unlikely enough! As I recall the energy needed for ignition is also lower in high O2 conditions.

Interesting link here about chamber treatment/fires; a few excerpts:

"Fire under hyperbaric conditions is always more intense because there is more oxygen available to support combustion. A rise from 21% to 28% in the oxygen percentage will double the burning rate. As the pressure is increased, the amount of oxygen available to burn increases. The increase is equal to the percentage of oxygen available multiplied by the number of atmospheres in absolute terms. For example, at a pressure of 4 ATA (equal to 30 m of sea water), the effective oxygen percentage would be 84% in compressed-air. However, it must be remembered that even though burning is very much accelerated under such conditions, it is not the same as the speed of burning in 84% oxygen at one atmosphere. The reason for this is that the nitrogen present in the atmosphere has a certain quenching effect."

"In monoplace chambers pressurized with 100% oxygen, a fire will be instantly fatal to any occupant. The human body itself supports combustion in 100% oxygen, especially at pressure. For this reason, plain cotton clothing is worn by the patient in the monoplace chamber to avoid static sparks which could be produced by synthetic materials. There is no need to fireproof this clothing, however, as if a fire should occur, the clothing would afford no protection. The only method for avoiding fires in the monoplace oxygen-filled chamber is to completely avoid any source of ignition."

__________________
Never forget that life is a finite resource.

Mdemon

Yes, a fire in a DS filled with 100% is going to be very bad...

__________________
www.southwestmafia.com

"small minds talk about people, Average Minds Talk About Events, GREAT MINDS TALK ABOUT IDEAS!"

The WRONG Attitude will get you killed.

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

Marc T

All of you know very well that an underwater decompression chamber witch is frequently used in cave diving is regulary vented to avoid accidentaly high CO2 but also O2 level.
So for me, after reading this thread, Im happy to know that its possible to use O2 in dry suit as emergency solution ( certainly better than having hypothermia or necessity to shorten a long deco because of trimix or worse heliox in drysuit when run out of air for inflate ), but ill never do that intentionaly.

I also think its perhaps better to open your O2 tank valve before connecting the hose at your dryduit

RonMicjan

as far as static electricity starting a fire, anyone looked at their gas bar-b-que or natural gas stove lately? it uses a quartz crystal to provide a tiny spark in the gas stream and will most certainly get a fire going. there are numerous cases of cigarettes starting fires in COPD patients clothing due to oxygen saturation of the clothing, I think the largest risk of using O2 in your drysuit would be after you took the shell off and were walking around in your woolies. the danger while diving would be minimized from lack of heat or ignition source. I never hear static crackling when I take my suit on and off. I dont think I would risk it unless it was an emergency and I had no other gas to use. My .02

__________________

iain-hsm

It would be interesting to know just how many dives you have on pure 02 suit inflation and to what depth…..and why? When Air or Nitrogen for that matter is just as “good” in molecular size.

When we test materials in oxygen under pressure to see the reaction we do the same test 20 times before increasing either the pressure or temperature or both. 1 fire in 20 tests is interesting, 3 fires in 20 and were thinking, 13 fires in 20 test time to choose another material but I never considered the luck of the Irish. How many dives was that again Barry? lol

Static discharge is the biggest risk IMHO. Remember when girls wore those fluffy nylon tops and the hairs on your arms tingled when you got a hand up. At the time I would have thought she was hot! As the video enclosed shows….. I was right.
(Yes, agreed I would have moved the car first too)

Attached Files

73099_staticelectricitygas[1].wmv (469.9 KB, 70 views)

Mdemon

Nice clip! Nylon undies? They'll have to come off...

The petrol pump example isn't quite the same though, is it? The spark there was into a mixture of highly flammable vapour and air. Any spark (if one could be generated) in an O2-laden DS will be in a mixture of O2 and damp solid.

I tried jabbing a lit spill at an old pair of socks in a bag full of O2 (the things I do for RBW!) On the second jab, flames leapt across the fibres sticking out from the material and then went out - there wasn't enough energy to burn the socks. (Yes, they were clean!) Will try doing the same with electrical ignition! Mwuhahahaaaaaaaaaaaaaa!

(PS Yes, the weather is crap and there's no diving anywhere. )

__________________
www.southwestmafia.com

"small minds talk about people, Average Minds Talk About Events, GREAT MINDS TALK ABOUT IDEAS!"

The WRONG Attitude will get you killed.

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