A fire door is an opening designed to prevent or slow the spread of fire and smoke within a building. These doors are installed in fire-rated walls and together they help keep a fire in check so occupants can exit safely. Fire door requirements are set by the National Fire Protection Association (NFPA). NFPA Standard 80 addresses fire door guidelines. This standard has been incorporated into most local building codes in the United States with little to no modification.
Fire ratings measure the amount of time that a door (or other rated object) is able to contain the spread of fire when tested according to NFPA guidelines. This means that a door with a 2-hour rating can be expected to resistant combustion for 2 hours in the event of a fire. A fire door will typically have 3/4 of the rating of the surrounding wall. For example, a wall with a 2-hour rating will usually contain doors equipped with a 90-minute rating. The duration of a fire rating can range from 20 minutes to 3 hours, though 20-minute doors are designed to block smoke rather than flames. The rating requirements for each type of door and wall in a building are set by the local fire marshal or building codes.
All fire-rated doors and frames must be equipped with a label indicating they have met all testing requirements. The label must be provided by a certified testing agency, such as Underwriters Laboratory, and may be embossed or mechanically fastened. Labels must indicate the door's duration (such as 90 minutes) and may not be painted over or tampered with in any way.
Door and Frame Requirements
Wooden fire doors must have a solid wood or mineral core, while steel doors will typically have a honeycombed or insulated core. The door should be prepped at the factory so that there is no more than 3/4-inch clearance between the bottom of the door and the finished floor. All hardware preps should also be made by the manufacturer. No holes larger than 1 inch in diameter may be drilled in the field without voiding the fire rating, and pairs of doors must be equipped with an astragal. Frames must be made from at least 16-gauge steel and should be prepped at the factory to receive hardware.
All fire doors must be self-closing and self-latching. This means that in the event of a fire, all of these doors will be closed and latched without manual intervention. This is accomplished through the use of a closer or spring hinge and a fire-rated lockset or exit device. Fire doors can never be held open with a door stop or any other device than a magnetic hold. The magnetic hold must be tied to the fire alarm so that the door will close automatically during a fire. Electric locks used on fire doors must be fail-safe, never fail-secure (door will be automatically unlocked during a fire to save lives rather than locked to protect property).
Louvres are permitted in fire doors only if they are labelled by a certified agency. The louvre must have a fusible link so that it closes to prevent smoke from spreading during a fire. Glass windows are also allowed, but may not be used in combination with a louvre. Doors with a 45-minute rating can have up to 1,296 square inches of glass and 90-minute doors can have up to 100 square inches of glass. Three-hour fire doors may not have glass windows.