A 3 hour door (180 min.) is typically required in 4 hour rated walls that separate buildings or divide a building into separate fire rated areas.
90 Minute doors (1-1/2 hr.) are required in 2 hour rated wall openings to stairwells, elevator rooms or egress through a building. 90 minute doors are also used in exterior openings where there is a potential for severe fire exposure from outside.
1 hour, or 60 minute assemblies are required on 1 hour rated walls that divide occupancies in a building.
45 Minute, or ¾ hour commercial fire doors are installed in 1 hour walls that act as room partitions or divide corridors. 45 minute doors are also used in exterior door openings where there is a possibility of light to moderate fire exposure from outside.
