Shaun Van Poecke wrote:
... The cyllinder ruptured in
an unusual way, splitting right down the side. ... the safety release valve
did not operate, ...

... the Co2 filled up the copper pot ... the welder climbed into the pot
... once he was
inside the pot he was overcome pretty quickly by dizziness and was unable to
get out. ...

Shaun - thanks for the real-world input. Too many of our posts are
speculation, sometimes not based on much knowledge.

While accepting that CO2 is more dangerous than I believed, I'm still
going to store my cylinder in the cellar. It's a probability thing
(like most things in life). The probability that there'll be a fire AND
the safety will fail is small enough for me. Likewise the probability
that my cylinder will leak fast enough to fill up my drafty basement is
small enough. It's a small cylinder.

Bob