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Influence of Gap Sizes Around Swinging Doors with Builders Hardware on Fire and Smoke Development

Fire Protection Research Foundation report: “Influence of Gap Sizes around Swinging Doors with Builders Hardware on Fire and Smoke Development”
Authors: Drew Martin and Brian McLaughlin, P.E.
Date of issue: March 2018


Swinging fire doors with builders hardware are critical components of maintaining building compartmentation. The ability for Swinging Doors with Builders Hardware (Chapter 6, NFPA 80) to restrict fire and smoke is determined by meeting the requirements in Chapter 6 of NFPA 80, Standard for Fire Doors and Other Opening Protectives (2016) and passing the NFPA 252, Standard Methods of Fire Tests of Door Assemblies (2015) standardized fire door test. The ability for swinging fire doors to resist the passage of fire and smoke and to comply with the applicable standards is affected by the gap sizes around the perimeter of the door, and as a result, the maximum allowable gaps around swinging fire doors are codified.

While the gap sizes identified in NFPA 80 have been written into the codes and standards for more than 50 years, recent requirements written to improve inspections, testing, and maintenance (ITM) have resulted in door clearance issues being one of the most frequently cited deficiencies. NFPA 80 currently allows a maximum bottom gap of 3/4 in. and a maximum of 1/8 in. for the perimeter (e.g. along vertical and top edges) of the swinging fire doors (with an additional 1/16 in. over-tolerance for steel doors). The clearance under swinging fire doors is frequently found to be greater than the maximum allowable gap size currently allowed by NFPA 80, due to irregularities in flatness and levelness of concrete slab floors at and around door openings.

The difficulty in achieving the 3/4 in. bottom gap instigates the question at the heart of this research, of what effect increasing the maximum allowable bottom gap size has on fire development.