I'm happy to be corrected, but I'd read that simply as the normal standard for that kind of equipment - e.g. BS EN 61439 for DBs or BS 5733 for a surface back box.. (Unlike some of the older kit - e.g. open backed fuses boxes - which were only intended to be fixed to non flammable surfaces). It's probably just duplicating the normal requirements but reinforces the point if someone's going down the 'equivalent level of safety' deviation route.

  - Andy.

Thank you. That does make sense. A quick Google of both of those BS's does reveal that temperature rise is one of the factors that should be considered in the design and testing. I guess that as long as I ensure all components are to the relevant  BS for the type, I should be OK. It does go on to define the BS for cables, conduit and trunking. It is only the electrical equipment section that is a bit vague. 

Thank you. That does make sense. A quick Google of both of those BS's does reveal that temperature rise is one of the factors that should be considered in the design and testing. I guess that as long as I ensure all components are to the relevant  BS for the type, I should be OK. It does go on to define the BS for cables, conduit and trunking. It is only the electrical equipment section that is a bit vague.