In article ,
Tim S writes:

a) What's celotex like to cut - use a knife or a saw?

I found a serrared breadknife was ideal.

b) In a fire, does it pose any risk of giving off noxious fumes?

I recognise the smell of cyanide componds (probably used to
foam it) when cutting it, so I would assume it gives off cyanide
when heated. Personally, I would not use it without a plasterboard
barrier between it and the house occupents. I tried lighting a
thin slither offcut and it burned. Others have said larger pieces
don't burn so well.

c) Does having an endothermic but still combustible material like
celotex packed around electric cables bother you?

Not if adiqately derated. I would not personally let PVC cables
come into contact with the expanded material incase there's any
long term degredation, not that I know of any. Where I've used
cable near Kingspan, I put it in PVC conduit, but that was more
for ease of rethreading cables if I wanted to chance the wiring
plan.

--
Andrew Gabriel