While many buildings have a 1- or 2-hour fire rating, 4-hour fire rated protection can easily save lives. To accomplish a four-hour rating, several elements must be considered.
Doors have a fire rating classification based on the fire rating of the wall into which they are installed. The location in the building and the current building code are used to establish the fire rating of the wall. The rating is broken down by time for steel fire doors. Typically, this includes 20 minutes, 45 minutes, 60 minutes, and 90 minutes. However, 3-hour fire rated protection is possible.
The amount of time a steel door can withstand exposure determines the rating. A 60-minute door is in a wall between rooms. A 45-minute door is in a corridor wall, room partition, or, sometimes, the exterior wall of a building if the fire exposure from the outside is moderate. For 3-hour fire protection, tight restrictions must be met for door size, glass size, and more. Typically, a door with a 3-hour rating is used to separate a larger building into several smaller fire areas.
To create a hollow section around an I-beam, quality insulating boards are installed with space left between the board and the beam on all sides. This fire-resistant material protects the column. In addition, the void space reduces thermal conductivity. Combined, the level of protection against a fire increases significantly.
To create 4-hour fire rated protection, things like cold-formed steel clips, gypsum board, and corner beads are included. At this level of protection, the thickness of the gypsum and the casing attachment meet tight specifications. Before the gypsum board is attached, steel clips are connected to the I-beam flanges, spaced every 4 feet from floor to ceiling. The ends of the flange clips attach to the steel to create the necessary air space.
For a building to have 4-hour fire rated protection, many other factors are involved.
As an example, glass, louvers, sidelight assemblies, door and window frames, door hardware, latching devices, hinges, and more play a critical role. Even doors in corridor walls used as an egress must have the proper smoke and draft control rating. These assemblies are thoroughly tested for both fire resistance and air leakage to ensure compliance with the current National Fire Protection Association code.