Fire rated doors are used in buildings to prevent the passage of fire and smoke between two compartments or areas. They are used as a passive means of protecting people and property from fires.
Doors and frames are given a fire-resistance rating after extensive testing by the Underwriters Laboratory in the United States, or another testing agency in other countries. Once tested, the door and frame receive a label that describes the amount of time the component is expected to provide protection when exposed to fire. When combined, all of the components of the door form an assembly that protects the opening. For this reason, all components of the door must include a rating label, including the door panel, the door frame, locksets, gaskets, hinges, and door protection plates.
A permanent label is attached to the door panel and the door frame, usually on the hinge side of both. Most other components have a UL symbol formed or stamped into the material to identify that they meet the UL requirements.
Local codes should be reviewed, but in general, rated doors must be self-closing and must have a positive latch. There are also limits to the size of glazing in the door, the width of gaps between door panels, the height of the door under-cut, and the size of air transfer grilles.