Sun Door and Trim

Fire Rating Information

Fire testing of doors and hardware and the resulting labeling authorities granted, is a complex subject that is better understood when basic rules and guidelines are applied. Requirements, regulations and laws governing fire rated openings can vary by location and municipality. We highly encourage customers with any questions to contact us.

The following information is for general reference purpose only, and should not be used to code compliance. Please consult your Authority Having Jurisdiction.

The fire rating classification of the wall into which the door is installed dictates the required fire rating of the door. The location of the wall in the building and prevailing building code establish the wall’s fire rating. The associated door ratings are shown below.

Hourly ratings
Steel fire doors are “rated” by time (in minutes or hours) that a door can withstand exposure to fire test conditions. Hourly ratings include 1-1/2-hours, 1-hour, 3/4-hour, and 1/3-hour,with the maximum rating required of any swinging type fire door being three hours.

Three-hour (180 minute) doors
 A door with a three-hour fire protection rating is usually found in walls that separate buildings or that divide a large building into smaller fire areas. The wall rating is four hours.

1-1/2-hour (90 minute) doors
Doors rated for 1-1/2 hours are found in 2-hour rated walls. These doors are commonly located in stairwells, or other enclosures of vertical communication through a building. They also occur in boiler rooms and in exterior walls that have potential for severe fire exposure from the outside the building.

One-hour (60 minute) doors
One-hour rated doors are used in walls between rooms, which are also typically one hour rated.

3/4-hour (45 minute) doors
Doors with 3/4-hour fire protection ratings are used in one-hour walls. A 3/4-hour rated door is found in walls of corridors and room partitions. A door with this rating may also be located in the exterior wall of a building subject to moderate fire exposure from the outside of the building.

1/3-hour (20 minute) doors
One-third-hour or 20 minute doors are used in one-hour walls. These doors are used for corridor applications and in other applications where smoke and draft control is a primary concern.

Twenty-minute doors tested without hose stream 
Doors and frames may also be rated as 20 minutes without a hose stream. These doors have successfully passed a 20-minute fire test, with the omission of the hose stream test, and bear a label that specifically states “Twenty- Minute-Rating Tested Without Hose Stream.” These doors may be provided with vision lights only limited in size by the door manufacturer’s fire labeling procedure authority. Assemblies identified as “Twenty-Minute-Rating Tested Without Hose Stream” should not be confused with 1/3-hour fire rated doors, which have been tested in accordance with the standard fire test procedure that includes the hose stream test.

Doors are rated for three-fourths of the rating of the surrounding wall: A 3-hour door is used in a 4-hour rated wall; a 1-1/2-hour fire door is used in a 2-hour rated wall; and a 3/4-hour door is used in a one-hour rated wall. The notable exception is that 1/3-hour rated doors are also used with one-hour rated walls. However, a door with a higher fire rating than the opening requires may also be used. For example, a door rated for 3 hours may be used in a 1-1/2-hour opening. All requirements for the 3 hour rating, such as maximum glass size, door size, and other restrictions for the higher rated door must be met.

As always, we recommend you contact one of the door & hardware specialists at Sun Door and Trim, inc. with any questions you might have.