Smoke Detector at Elevator Door & at Ceiling?

9/21/2021

A project I'm on has a lobby area with a 35-foot tall ceiling next to the elevator door.

NFPA 72-2010/2013 Section 17.7.3.1.3 and 17.7.3.1.4 allows a smoke detector within 60-inches of the top of each elevator door to protect the opening. This can be used for elevator recall.

In addition to this smoke detector, do I also need one at the ceiling (35-feet) for normal coverage?

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4 Comments

Alex Riley

9/21/2021 07:28:23 am

Hi Anonymous,

Great question. I’m having trouble finding a code section to back my claims completely, but here’s what I got:

NFPA 72 (2019) 17.7.3.1.1 states that “the location and spacing of smoke detectors shall be based upon the anticipated smoke flows due to the plume and ceiling jet produced by the anticipated fire, as well as any pre-existing ambient airflows that could exist in the protected compartment”.

NFPA 72 (2019) 21.3.5.1 and 21.3.5.2 state that a smoke detector must be located within 21 feet of the centerline of each elevator door, and for ceiling configurations exceed 15 feet in height, the design shall follow Chapter 17. Section 17.7.3.1.3 states that if the “intent is to protect against a specific hazard”, smoke from an elevator for elevator recall, “detectors shall be permitted to be installed closer to the hazard in a position where the detector can intercept the smoke”.

From both of these code sections, I believe that for your situation, you are required to install smokes above the elevator for recall, and additional smokes at the ceiling to protect against the anticipated smoke flows due to the possible plume form a fire originating within the lobby.

Looking forward to seeing what everyone else digs up.
Alex

schulman

9/21/2021 08:10:06 am

I agree with Alex but not based on the code.
Seems like two covers the space better AND provides for the specific elevator shaft coverage. I'm not trying to save money on Fire Alarm systems. Pretty sure the AHJ isn't going to be upset with "possible additional coverage".

9/21/2021 08:28:50 am

NFPA 72:17.4.7
States that if the intent is to initiate action when smoke or fire threatens a specific object or space, the detector shall be permitted to be installed in close proximity to that object or space.

A17.4.7
This sections indicates that areas that do not require full area protection but do require detection can have coverage within close proximity to protect against fire or smoke. Elevator lobbies with ceilings greater than 15' allow for the detector to be within 60" of the top of the elevator.

DTW FPE link

9/21/2021 02:22:38 pm

In the early days of elevator recall it was not uncommon to install the smokes just above the elevator door opening as the idea was to protect the elevator shaft from ingesting smoke if it were to open in a smoke filled lobby. While more detectors might be better for finding smoke in a lobby, it doesn't help the function of the elevator lobby detector.

Also, who would want to be the one servicing a detector 35 feet in the air? In the end it might end up being a beam detector from a servicing and coverage aspect...not a inexpensive solution.

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Smoke Detector at Elevator Door & at Ceiling?

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