On 22/10/2015 14:31, NY wrote:

Mind you, even inert compressed gas is dangerous. My A level chemistry
teacher had taught "in industry" before becoming a teacher and he worked
in a building near Heathrow. One of the young engineers (who should have
known better) tried to unscrew the main valve-plus-gauge unit from a big
4-foot nitrogen cylinder, possibly when he should have been unscrewing a
hose from it. The valve blew off, shot through the ceiling and was found
several miles away just inside the perimeter fence of Heathrow by a
routine security patrol. The cylinder was pushed through the floor and
buried itself in the concrete floor below. No trace of the engineer was
found. And that's due to pressure alone - nitrogen is not flammable.

That doesn't sound quite right. He might have lost a hand or an arm or
been killed by it if very unlucky but he would still be there.

I have known an industrial accident where an unchained nitrogen cylinder
fell over and knocked the valve clean off. The valve went through a few
brick walls and several asbestos process sheds before coming to rest.
Fortunately it didn't intersect with anyone on the way. The cylinder
suffered a version of the hose pipe instability and scudded round the
shed spinning horizontally as it went. Doing a fair amount of damage but
again missing people. The unfortunate engineer was deaf for a couple of
days and probably had long term hearing loss.

At university we had someone use ordinary rubber pipe and no regulator
on a 2000psi gas bottle. He cracked the valve open a little and saw the
tube instantly blow up to beachball size followed by an enormous bang
and then silence. ISTR it took a week for his hearing to return.

--
Regards,
Martin Brown