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Interpretation #7711

Original Request

  • Date: January 19, 2016
  • Requested By: Todd Miller
  • Requester E-Mail: todd.miller@chehayeb.com
  • Code Version: 2014
  • Code: BUILDING
  • Code Description:
  • Chapter:
  • Section: 907.3.1
  • Topic: Smoke detectors in supply and return

  • Question: Are duct mounted smoke detectors required in both supply and return air ducts in units with 2000 cfm and above?

Answer on 01/19/2016 at 2:34 PM

This item went before the FBC in the Fall of 2015, the
commission stated that there was "not a conflict" between
the building and fire codes. That leaves the interpretation
up to the local AHJ. Building requires it in the return and
fire requires it in the supply........ So, if there is no
conflict..... it is required on both sides.

Commentary:

It should be noted that FBC Code does not reference NFPA 90A, but NFPA 90A still requires smoke detectors in the supply. FBC diverges from NFPA 90A because the International Code now also diverges. Both the International Code and the FBC require smoke detectors in the return. The Building Departments generally require compliance with FBC and the Fire Departments usually require compliance with NFPA 90A, so as a practical matter there are two detectors required, one in the supply and one in the return. This is true, even though analysis of unreferenced NFPA 90A is (now) beyond the scope of this forum. One detector (The one in the return) gives "earliest warning" of a fire in the space; the one in the supply heralds a fire in the air handling unit or fan. Bottom Line, put 'em both in.