HOURS 7:30AM - 4:00PM MON - FRISteel fire doors are covered by four ratings. These ratings are determined by exposure limitations of the door itself. The maximum requirement for any steel fire door is an exposure rating of 3 hours. The other ratings are 11⁄2 hours, 3⁄4 hours, and 1⁄3 hours or 20 minutes. Fire door openings are classified by their locations in the building. The location determines the length of exposure protection required, based on the potential fire hazard of that particular area. The five openings classifications are shown in the table along with the four door ratings and maximum amount of glass in square inches allowed for each classification. There are no hourly ratings for a basic fire frame, unless the labeling on the frame specifically states that the frame is rated for something less than 3 hours. Frames used in masonry walls may be used with a maximum 3 hour fire door while frames used in drywall are intended to be used with a maximum 11⁄2 hour fire door.
