Visual characteristics to look for are, normally fitted with three hinges, fitted with a self-closing device, intumescent strips, and cold smoke seals (which can be retro fitted). The newer doors may have colour plugs inserted into its edge, which denote the standard of the door, e.g white circle with red dot is a Fire Door which requires intumesvent materails to be fitted, where a white circle with green dot may not require these materials. These types of doors will relate to stability and integrity.

Thanks guys

I have since had a look at this webpage http://www.firesafe.org.uk/fire-doors/ and the section on the
TRADA Q-Mark fire door scheme.

Thanks again