How do I know if an interior door is a fire door?

I'm looking to replace an interior door with a new door that is more aesthetically pleasing but am unsure if the existing door is a fire door. How would I tell if it is?

The existing door is 45mm thick and has three hinges with 15 panes of steel re-inforced glass, although there is no auto-closing mechanism and no markings on the top or bottom to indicate any special type of door. There is also no intumiscent on the door or the frame.

The door may have a small, coloured plastic disc near the top hinge

Most modern doors will have a tamper-resistant label on the top edge - BWF-CERTIFIRE from the BWF - www.bwf.org.uk

From your description the door is a fire door, but the doorset (whole installation) is not up to todays standards

Domestic fire doors are normally only in flats or on houses of three-storeys or more and on certain rooms.

only one way to find out!

jumbob said:

door is 45mm thick and has three hinges with 15 panes of steel re-inforced glass

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and I expect it is surprisingly heavy. So yes it is

anyway, you decide if you need a fire door regardless of what sort the old one is.

glazed fire doors are incredibly expensive if they use unwired fire glass