smoke detector placement

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nizak

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Has anyone here who does residential work ever been called on having a smoke detector located too close to an air duct, warm air, return air etc? When I roughed it in 2 months ago, I was told that all the HVAC rough in was complete, I come back now to trim it out and I've got diffusers in the ceiling 8 inches from the devices. Manufacturers specs say 36" away from any HVAC, anybody here ever run into this problem? I would assume the building official will make the call, smokes fall under their domain here in MI.
 
if the manufacturer's instructions say don't put it there, maybe that's because it won't work propely if you put it there. why put something that is a life-safety issue in wrong ?
 
nizak said:
Has anyone here who does residential work ever been called on having a smoke detector located too close to an air duct, warm air, return air etc? When I roughed it in 2 months ago, I was told that all the HVAC rough in was complete, I come back now to trim it out and I've got diffusers in the ceiling 8 inches from the devices. Manufacturers specs say 36" away from any HVAC, anybody here ever run into this problem? I would assume the building official will make the call, smokes fall under their domain here in MI.
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I am pretty sure it is only 36" from a cold air return not the feed ducts. I have had the same problem as you -- luckily the inspector caught t on the rough in. Of course I had to move the SD.
 
Watch out for place ment near bath rooms as well. Read your instructions and it should recommend from 12" to 36" away from bath room, cant remember which.
 
Check out the FAQs on smoke detectors.

I'd say that even if the AHJ is not enforcing NFPA 72, they are obliged to consider the instructions included with the smokes per 110.3(B) of the NEC.

Edit: One thing that does confuse me, though, is I just intentionally installed over a dozen smokes on the return air grills at the commercial office building I'm working at, per the prints, and the Fire Inspector expected to see them and ensured they were operating correctly. We got our first dirty smoke reported in the system yesterday at one of those locations...? :confused:
 
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georgestolz said:
Check out the FAQs on smoke detectors.

I'd say that even if the AHJ is not enforcing NFPA 72, they are obliged to consider the instructions included with the smokes per 110.3(B) of the NEC.

Edit: One thing that does confuse me, though, is I just intentionally installed over a dozen smokes on the return air grills at the commercial office building I'm working at, per the prints, and the Fire Inspector expected to see them and ensured they were operating correctly. We got our first dirty smoke reported in the system yesterday at one of those locations...? :confused:
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The code says they must be 36" from forced air ducts, which a return is not.
 
brantmacga said:
The code says they must be 36" from forced air ducts, which a return is not.
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According to what I wrote before (I had the online version of 72 open when I wrote that), it said return, supply, or ceiling fan. I can go double check that real quick.
 
brantmacga said:
The code says they must be 36" from forced air ducts, which a return is not.
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IMHO a return IS a forced air duct, the force is just going the opposite way!

George- here in FL the smoke detector for an A/C unit goes in the supply. I believe that was a recent change and of course which ever of the too many versions of the code(s) you are enforcing may make requirements different.
 
iwire said:
I think that may be a misconception.
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From the directions of a Kidde smoke alarm; it says they should not be installed within 3' "of forced air supply ducts". The return is not a supply duct. I looked up the online version of NFPA 72, and when it talked about placement for detectors it uses the wording "shall not be located directly in the airstream of supply registers". That was 2007, NFPA72,- 5.7.5.3.2. Unless the manufacturer's instructions prohibit you from putting it near the return, you're okay to place it there.
 
brantmacga said:
The code says they must be 36" from forced air ducts, which a return is not.
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Let me see...you can't push dirty air thru a smoke but it's ok to pull dirty air thru a smoke? not. Return air is forced air. Passive thru wall are also forced air. 3' from ceiling fans (forced air)
 
Just thinking, but wouldn't it be beneficial if it was away from the forced ducts (the ducts heating/cooling) a room, as apposed to the return which are pulling the air in - say in a fire when the smoke's rising the furnace is running and sucking air in and the smoke is close to it, it'll PULL the smoke up close to the detector? As apposed to the forced ducts which would PUSH the smoke from the detector? I've always assumed if it was close to a return air (assuming the return is in the ceiling) it would be one of the faster areas to receive the smoke then letting it just build up until it hit the ceiling...
 
Cavie said:
Let me see...you can't push dirty air thru a smoke but it's ok to pull dirty air thru a smoke? not. Return air is forced air. Passive thru wall are also forced air. 3' from ceiling fans (forced air)
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Maybe, but its not forced are supply. By definition, the return is not a supply register. The way the code is written, it does not prohibit installation within 36" of the return. If the CMP didn't want it there, it would say "forced air supply and return".
 
georgestolz said:
That's great, I can't see the bottom of the page. :rolleyes:
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You may be able reduce your font size in Safari, and more
of the page will be there. The font may be too small to
read though...
 
Cavie said:
Let me see...you can't push dirty air thru a smoke but it's ok to pull dirty air thru a smoke? not. Return air is forced air. Passive thru wall are also forced air. 3' from ceiling fans (forced air)
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Hi Cavie,

Definitely an interesting comment. What Kidde, BRK, and other alarm mfrs. do not mention is that generally in home construction, the CAR (cold air return) is not installed in bedrooms. The HVAC system pulls the 'cold' air back into the furnace via a centrally low near floor mounted CAR which is generally in a hall way or common area.

Ceiling CAR's were common in furnace supplied systems a long time before the HVAC technology developed to where A/C-heat pump units came along and required better circulation strategies. So the return supply George mentioned is really more commercial practice than residential methods.

The Kidde instructions of placing the detector in the center of the room is somewhat contradictory of Life-Safety practices that generally require a bedroom to have a detector close to the transom or door header. I am surprised Kidde made that recommendation, reason is that a hallway fire ceiling smoke will filter into the bedroom from the door to set off the alarm a lot sooner than a center room mounted unit.

There may be another reason that they are aware of and I have not experienced since smokers hit the market in the early 70's. I do know that mfrs. are producing combination photo-ion units that cover the ignition spectrum for earlier warning safety in modern residential applications. rbj
 
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