AskCodeMan

Codeman,
I was told today by a HVAC contractor that a smoke detector must be 36" from the return (both are on the ceiling and 20" apart). This is the first time I have ever heard of this and I can't find anything in the code book to confirm this.

So two questions, is this a code violation (2006 IRC) and what would be the issue with this set up?

Hi Chris,

That is found in the installation instructions for the smoke detectors. The smoke detectors need to be at least 3 feet from an air disturbing source, which would include returns, supplies, and the ends of the blades of ceiling fans. Note that "air disturbing source" is the term I use to describe sources which disturb the air and which the smoke detectors need to be away from, I have forgotten the precise wording in the installation instructions as the various installation instructions used slightly different wording - I just found that "air disturbing source" was descriptive and readily understood as to why it should not be close to the item disturbing the air, you want the smoke to get to the detector, not be sucked or blown away from the detector.

I have seen some smoke detectors in years past which said 5 feet from the air disturbing source, but recently it seems that 3 feet is the new standard clearance.