To twsutton.
An interesting enquiry!
FIRE RESISTANCE OF DOORSETS.
A doorset is defined as an assembly, [ including door, frame and guides], for the purpose of closing a permanent opening in separating elements. For the purpose of British Standards, the term doorset includes shutter assemblies, but excludes fire dampers incorporated into ducts. In England & Wales Approved Document B, [ to the Building Regulations] , gives the specifications of FIRE DOORS. The doors are identifed under their performance, UNDER TEST, for integrity under a period of minutes. the minimum FR of doors in terms of integrity is given in TABLE B1 of Approved Document B.
IDENTIFICATION OF FIRE DOORS.
Fire Doors should be identified by the initials FD followed by the performance in minutes that the door should achieve, when tested for integrity only. where the door should also resist the passage of smoke at ambient temperatures the suffix " S " should be added to the identification.
PRACTICAL APPLICATION.
From the point of view of an experienced FPO, doors that may meet the requirements are usually assessed by experience, by checking widths, the feel of the door by weight and by its density. However if there is any doubt then certified documents should be insisted on being provided.
I hope this helps
Conqueror.