s, I am sorry that I was not specific. I was referring to your statement about metals burning ... though on reflection I just need to go back to secondary school Chemistry to realise that metals do indeed burn!
And hence a thin steel box is non-combustible but is not fire-proof, fire can effectively pass from one side to the other without the steel burning if flammable materials are in contact with it.
That's because it's finely divided i.e. has a large surface to volume ratio so a lot of it is exposed to the air at once. If you've got a finely shredded DB, it's not the flammability you need to worry about but the size of the rats...
Anyway I installed my last plastic DB about 10 years ago and haven't touched a domestic install since. If I did, it would be steel all the way.
I really think they've gone about this new reg the complete wrong way, Imo they should of been including the need for smoke/heat alarms near to consumer units. Could even have them connected to a contractor to cut the supply.
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