Fire 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 opening classifications are shown below. Fire-protection ratings tested and classified by: Warnock Hersey-WHI or Underwriters Laboratories- UL. The local Authority Having Jurisdiction must be the final authority on fire door assembly issues.
Note: Most exterior doors do not require fire rating, unless there is the potential for fire exposure from the outside of the building. See Flush Metal Doors for non-rated doors, which are made from the same construction as a fire-rated metal door.