Fire Door Classified OpeningsFire door openings are classified by their locations in a building. Location determines the length of exposure protection required, based on the potential fire hazard of that particular area. The six opening classifications are shown below. The maximum amount of glass allowed in a Fire Door varies. Call us for info on allowable glass.

Class Door Rating Description and Use
A 3 Hour (180 Minutes)
These openings are in wall that separate buildings or divide a single building into designated fire areas.
B 1 1/2 Hour (90 Minutes) Openings of this type are used in enclosures of vertical communication or egress through buildings. Examples include stairwells and elevator shafts.
C 3/4 Hour (45 Minutes) For use where there are openings in corridors or room partitions.
D 1 1/2 Hour (90 Minutes) This opening is in a wall where there is the potential for severe fire exposure from the exterior of the building.
E 3/4 Hour (45 Minutes) This opening is in an exterior wall that has the potential to be exposed to moderate to light fire from the exterior of the building.
– 1/3 Hour (20 Minutes) These openings are in corridors where smoke and draft control is required.