Smoke detectors and door release requirements for smoke barriers
BY WAYNE D. MOORE
Doors used to protect openings in smoke barriers provide an integral safety feature in every health care occupancy. The 2016 edition of NFPA 72®, National Fire Alarm and Signaling Code, provides the requirements for the installation of smoke detectors for door release service. Actuation of smoke detectors release the doors and help ensure that they close whenever smoke invades the area near the door.
Where the release of the door takes place exclusively from the smoke detector, using internal relay contacts, a nationally recognized testing laboratory must have tested and listed the detector for releasing device service.
The number of smoke detectors required, and all of the spacing requirements found in sections 18.104.22.168.2 through 22.214.171.124.6, apply when the detectors are used for the singular purpose of smoke barrier door release. If the doors must close in response to smoke flowing in either direction in the corridor space, the code contains specific requirements for detector location. The code also provides graphics of required locations that match the requirements, based on the depth of the wall section above the door and the number of doors in the doorway. If the depth of wall section above the door is 24 inches or less, for example, the code requires one ceiling-mounted smoke detector on one side of the doorway only. If the designer specifies the use of wall-mounted detectors, then the code requires two detectors, one on each side of the doorway.
If the depth of the wall section above the door is greater than 24 inches on one side only, then the code requires only one ceiling-mounted smoke detector on the higher side of the doorway. However, if the depth of wall section above the door exceeds 24 inches on both sides of the doorway, then the code requires two ceiling-mounted or wall-mounted detectors, one on each side of the doorway. When the depth of the wall section above the door exceeds 59 inches, the code requires the performance of an engineering evaluation to determine the need for additional detectors. Finally, when the design specifies the use of a listed door frame–mounted smoke detector or a listed combination integral detector-door closer assembly, the code requires only one such detector when installed according to the manufacturer’s published instructions.
The locations for ceiling-mounted smoke detectors installed on a smooth ceiling for a single or double doorway must match the centerline of the doorway no more than five feet from the door and no closer than 12 inches to the doorway. Regardless of the depth of wall section above the door, if the door release intends to prevent smoke transmission from one space to another in one direction only, detectors located in the space that will confine the smoke must meet the same requirements as outlined above for the doorways leading from that space. When a space includes multiple doorways, the code requires additional ceiling-mounted smoke detectors depending on the number of doors and the spacing between them.
Given all of this, it’s easy to see why detector spacing for the specific purpose of controlling smoke spread in corridors or smoke compartments can prove somewhat intimidating. But smoke detectors included as part of a code-compliant open area detection system covering the room, corridor, or enclosed space can satisfy all these requirements for smoke barrier door release service. In other words, when smoke detectors protect a hallway or other enclosed space using the open area spacing of the code, none of the requirements in sections 126.96.36.199.2 through 188.8.131.52.6 applies.