Is it legal to place a smoke detector next to a sprinkler head?

Fire Alarm General Discussion
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I’ve seen a lot of installations where some smokes are placed in the range of coverage of sprinkler heads. Is it legal to do so?

I suppose that if a fire occurs and the sprinkler head bursts, the water will definitely go into the smoke detector and short out the IDC/SLC, rendering all the device in the same circuit inoperable. Even if short isolators are used, the disablement of devices near the outbreak point will certainly have a negative impact on the effectiveness and accuracy of automatic fire detection and control.

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Typically the smoke detectors and a sprinkler’s waterflow switch are connected to the same system so if a fire were to outburst the alarm system would be activated and most likely the detector can easily be replaced. Smoke is received much faster than the heat from the fire itself so if the detector needs to trip the system the detector would just get damaged anyway. Therefore it is perfectly safe to place a detector next to a sprinkler head since the alarm system would at least need to be tripped automatically in case if a fire were to burst out.

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“Legal” in this case would mean AHJ approved. Therefore, it would depend if the AHJ allows it.

As far as I know, there is nothing in NFPA 13 or NFPA 72 that explicitly prohibits placing the two within close proximity to each other. In fact, if one activates, it already does the job of protecting the building/occupants of a single fire.

I would be more concerned about how the smoke detector would obstruct the spray pattern of a sprinkler head (see Chapter 10 of NFPA 13 for standard sprinkler heads). Certain provisions require sprinkler heads to have clearances so that the spray pattern is unaffected – if a fire were to start, a spray pattern that is not according to its intended design will make a difference in how it can suppress the fire.

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Even if it’s legal in the AHJ where you’d be at, I should’ve mentioned that it’d still be a good idea to at least have it over a few centimeters away from any sprinkler head that would spray in it’s direction to be able to put out the fire.