pure o2 rebreather question...

[Kimsey0]

Ok, near the valve on a pure o2 tank, if you touch around that area then turn on the valve, it will create a small explosion due to human body oils, i understand it's not enough to kill you, yet why is it when a person is using a full face mask with an o2 rebreather the pure o2 doesn't react with the oils on his/her face to create an explosion? This question has been nagging at me for days and i can't figure it. Funny no pure o2 rebreather articles that i've read cover this. Any answers much appreciated.

 

[caveseeker7]

Pressure. Stuff the FFM into a tank, add 3000PSI of O2 and duck. Fast.

 

[Mako Mark]

it takes only a little bit of pressure.

I once saw guy cause an explosion on a welding set by putting his thumb over a pinhole leak in the o2 hose. There was a funny POP sound then he was running around sucking his thumb. I am not sure what the pressure in those hoses are, but I am sure that it is not much.

Be careful arond O2 under pressure, it doesnt give much warning.

 

[Kimsey0]

Oh, pressure. That explains alot really, given that there's probably 0 psi of pressure directly on the diver's face. Thanks for the replies you two.

 

[caveseeker7]

Usually there is ambient pressure at the diver's face, 1 ata at the surface, up to 1.6 ata at 6m/18ft. in normal diving (higher for short periods in the military during evasion).

 

[schford]

o PSI - absoutely zero pressure hmm would that be a vacuum - would our eyes get sucked? ewwwww

 

[Kimsey0]

o PSI - absoutely zero pressure hmm would that be a vacuum - would our eyes get sucked? ewwwww

I think you know what i meant schford.

 

[schford]

I think you know what i meant schford.

Sorry Kimsey0 - Was just a Joke - my bad sence of humour :11: I know thats not what you meant!!

 

[Kimsey0]

it takes only a little bit of pressure.

I once saw guy cause an explosion on a welding set by putting his thumb over a pinhole leak in the o2 hose. There was a funny POP sound then he was running around sucking his thumb. I am not sure what the pressure in those hoses are, but I am sure that it is not much.

Be careful arond O2 under pressure, it doesnt give much warning.

Yeah, i think welding hoses are under something like 25 psi of pressure, if they're on a regulator, apparently 25 psi is alot more than 1.6 ata i'm honestly not up on translating pressures, another thing is counterlungs until recently were rubber, and welding hoses are made of rubber usually and rubber combusts with o2 under pressure so different "fuels" must combust at different pressures. Honestly this is a very elusive subject that's hard to get info on on the internet, but some of it's vital if you're working on your own rig. I'd be nice if a person could find a data sheet on the combustion pressures. Oddly enough most of the websites/books that i own make it out like it's not much of an issue in the breathing loop, just in the regulator... *shrug*

 

[Dive Bear]

Before you blow yourself up (or get your eyes sucked out) get a copy of Vance Harlow's Oxygen Hacker's Companion from Airspeed Press.

That way, you'll be able to blow yourself up the right way.