Hi, I don't know about insurers will or will not insure ect.
In the event of a fire, any gas cylinders can explode and any unknown gas cylinders should be treated as acetylene cylinders. Acetylene has flammable limits between of 2 to 82 percent of air.
"Acetylene gas under pressure becomes unstable and is regarded as an explosive. Cylinders must never be subject to intense heat or severe physical impact as the rise in temperature and pressure may cause the Acetylene to thermally decompose."
"Despite the decomposition of the gas and the increase in temperature and pressure the cylinder may seem to be in a normal condition. If the cylinder it is moved it may detonate and anyone nearby may be fatally wounded by the blast." (Quotes taken from my notes in my Oxyfuel Gases Safety Awareness course)
There is a 200 meter exclusion zone around any Acetylene gas cylinder for 24 hours in a fire for the very reason of the potential thermal decomposition and detonation of these cylinders.
As far as I'm aware, the fire brigade will not enter a burning building with gas cylinders inside if they cannot be told exactly where the cylinders are located, unless there are persons inside. But other factors will also stop them going in.
Regards Nick.
P.S. Terry's idea about having acetylene (and any other flammable gases) in a lean-to or any other out side ventelated cover and the gas piped into the workshop, is the best and safest way of using these cylinders
Edited By Nicholas Farr on 10/11/2012 13:40:43