please advise on the technical difference between a 1 hour fire door and a 2 hour fire door, besides the obvious 1hr fire rating.

thanks

Most fire door sets are a composite construction and finished with a timber veneer so visually they all appear to be the same. Its the construction that achieves the fire resistance and the manufacturers will not reveal this for obvious reasons. The only way to determine the fire resistance is to purchase certified fire door sets with documentation, labels or in some cases plastic plugs. The thickness of the leaf of the door may be an indication but not always and sometimes what appears to be a timber fire door in a metal frame can indicate a two hour fire door. I am afraid its all about third party certification and of course you can have metal or glass fire doors.

Check out http://www.firesafe.org.uk/fire-doors/ for more information.