Fire development, smoke movement and ability of fire door to meet the test standards are affected by the gap sizes around the perimeter of the door, within the frame and between the bottom of the door and floor. Hence these gap sizes are regulated and the current regulations in NFPA 80 for the door clearances are from information and data gathered several years ago. Door clearances are one of the most frequently cited deficiencies on swinging doors with builders hardware. In the 2016 edition of NFPA 80, Section 18.104.22.168 addresses the clearance dimensions for gaps between the door leaves and door frames for fire-rated door assemblies with steel, and wood doors, and includes provisions for door assemblies of other construction. The clearance dimension allowed for steel doors (rated up to 3 hours) and 20-minute wood doors installed in hollow metal door frames is 1/8-inch (+ 1/16 inch). A maximum clearance dimension of 1/8-inch is permitted for wood doors fire-rated more than 20-minutes and fire door assemblies with doors and frames of other construction (of any level of fire rating). Further, paragraph 22.214.171.124 permits a maximum clearance dimension of 3/4-inch under the bottom of a door, regardless of the construction of the door. Of the clearance dimensions around the perimeter of door leafs, the clearance under the doors is the most difficult to comply with when the doors are installed since the floor itself is not a component of the door assembly. Frequently, the surface of concrete floors at door assemblies is not level (across the width of the opening) or might have low spots under the door. The surface of the floor creates situations where the clearance dimension under the door is greater than 3/4-inch and therefore non-compliant with NFPA 80 requirement. Additionally, current fire door tests in NFPA 252 use a clearance dimension not greater than 3/8‐inch under the door(s), which is not consistent with NFPA 80 allowance of a maximum of 3/4‐inch and, more importantly, is not realistic to replicate in the field. Hence it is important to have a deeper understanding of the impact of gap sizes on fire development and smoke movement.
Research goal: The overall research goal is to determine the effect of an increased clearance dimension around single and double egress swinging fire rated wood and steel doors on fire development within the compartment and the smoke movement. Of specific interest: (1) to study the influence of larger clearances under doors; (2) to study the effect of additional 1/8-inch clearance along the vertical and top edges of the door leaves on door assemblies on fire and smoke development.
Download the project summary. (PDF)