Hi Bob,
My experience has been a bit different to yours. Regarding CO2 cyllinders
as a potential source of explosions, about 3 weeks ago my best friend was in
his caravan when it caught on fire. he had a mid size co2 cyllinder inside,
which ruptured. The temperature was extremely hot inside the van, hot
enough that it melted all the aluminum sheeting. The cyllinder ruptured in
an unusual way, splitting right down the side. It blew through the
relatively thin wall and landed about 30 feet away on the road. I was
outside the van trying to get in when it exploded. the safety release valve
did not operate, there is a current investigation being made by BOC as to
why.

Regarding risk of asphyxiation, this is a very real risk. I work in mount
isa australia, a fairly large mining town. The company i work for is
frequently doing confined spaces work inside tanks and other vessels. we
follow standard procedures of using forced fan ventillation and extraction,
an air sniffing machine and having a spotter who is qualified to do a
confined spaces recovery in case of the worst. We have thankfully never
experienced an incident, but we do receive safety bulletins from other
companies as part of our safety network. I have seen quite a few bulletins
concerning deaths in these types of situations. One particular case that
comes to mind ivolved the death of 3 people - the person in the confined
space, and the deaths of two people trying to recover him.

We did have a near miss last year while welding inside a copper smelting
pot. These pots are used by the mine and hold about 90 tonnes of copper.
You climb up a ladder to get inside, its like sitting in a giant coffee cup.
We weld tham back up with a dual shield filler with CO2 as the gas. The two
staff welding the pot had gone for lunch and had turned off the extraction
system for some peace and quiet. What had happened was the valve on the
welding unit which controls the gas flow had stuck 'on'. gas was
continuously pouring out the end of the nozzle at 20 litres a minute.

They had a fairly long lunch and there wasnt much wind blowing that day.
the Co2 filled up the copper pot much like water - displacing all the
breathable air. The guys came back, and the welder climbed into the pot
while the other fellow went to turn the extractor back on. once he was
inside the pot he was overcome pretty quickly by dizziness and was unable to
get out. Thankfully the extractor system came on and fresh air was forced
inside. It was a big wake up call for us.

Ive never actually breathed Co2 myself, though i have done my share of
confined spaces welding. Im very concerned about following the right
procedures for this type of work.

Best Regards,
Shaun

"Bob Engelhardt" wrote in message
. ..
Newshound wrote:
Not quite the only issue. Even a CO2 tank in a fire is a bomb,...

I don't think so - they have pressure relief valves. Plugs, actually,
IIRC.

And if you happen to have confined spaces, particularly a cellar or
similar, there is a real asphyxiation risk from a leak. ...

I don't think so - breathing just a little would be so distressing that
you'd immediately get-the-hell-out. It's the rise in CO2 concentration in
our lungs that makes it so hard to hold your breath for very long. There's
still plenty of oxygen in your lungs but the rising CO2 says: BREATH!
BREATH!! You start experiencing that in your cellar and you'll be out of
there long before asphyxiation is a risk.

Bob