On 7 Feb, 22:45, Mike wrote:
http://news.bbc.co.uk/1/hi/world/americas/8503142.stm

Has Drivel gone on a holiday overseas or are catastrophic floods more
his line?

--

I wonder what the truth of the matter is? In the UK non domestic
purging is strictly controlled and with pipes of the size indicated
would normally be air - inert gas (usually Nitrogen) - combustible gas
to prevent any possibility of an explosive mixture within the pipe.
Speed of purging (velocity within the pipe) is also critical so as to
minimise mixing or diffusing at the interface.
If the Merikans have similar standards it may be that someone cut
corners. I wouldn't worry about it happening over here with trained
operatives.