Which of the following installations can be acceptable for smoke detectors?
a. Wall-mounted smoke detector located 3 inches down from the ceiling
b. Smoke detector located at the bottom of a shallow beam
c. Ceiling-mounted smoke detector located 2-1/2 inches from a wall
d. Smoke detector located adjacent (1 ft) to a supply diffuser
Solution | Posted 06/25/18
Please note: this question is no longer acceptable based upon the re-introduction of NFPA 72-2016 to the PE Exam.
In order for this question to be acceptable by NFPA 72, it would have to read "which of the following installations is not acceptable for smoke detectors?"
NFPA 72-2010 edition addresses updates from a Fire Protection Research Foundation and Kemano Study "Smoke Detector Spacing Requirements Report (2008)", that determined mounting within 4 inches of a flat ceiling/wall corner for smoke detectors is acceptable, and that detection performance does not depend upon the 4-inch separation.
The NFPA Fire Protection Handbook appears to not incorporate this update, as Figure 14.2.16 on page 14-26 of FPH matches the 2007 Edition of NFPA 72 which infers that all detectors (smoke and heat) are not permitted within a 4-inch zone.
As a side note, if a conflict like this exists between two required references (where solutions could be different based upon which required reference is used), then the question would typically not be used or would be removed from use on the exam. I've kept the solution here for educational purposes.
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