ECN Forum Forums Code Related Discussion NEC & other Code issues where to mount Smoke detector in room with ceiling fan

Adding smoke detectors in the bedrooms of a 50 year old house. One bedroom has a ceiling paddle fan in the center of the ceiling. A reversable fan. My concern is that the fan will blow away any smoke from the detector. Where should I place the smoke detector? 5 feet away on the ceiling, or maybe 10 feet? Or on the wall? Or is this a non-issue, being that smoke will find the detector anyway with or without the fan running?

I'd say it's a non-issue.

What do the installation instructions say? In my opinion, the fan will create a significant delay in the operation of the smoke detector in the event of a fire. There are rules that say a smoke detector should not be placed within 3' of an air discharge register. I'm not sure about a rule for fans, but if the fan is in operation it will dilute the smoke and retard its flow to the detector, both of which will increase the response time. I would consult with the local fire marshall.
Don

hmm, seems i don't have any Firex instructions on file, yet i recall a similar distance

4' from the edge of the fan blades comes to mind

obviously, positioning closer to a door would insure greater efficy for external threats...

Sparky,

Don't you put smokes outside the Bedroom too?

Bill

While I agree that an operating paddlefan will delay the alarm of a correctly placed smoke detector, I don't think anything will mitigate the delay short of not running the fan.

Paddlefans are intended by design, sizing and placement to roll the entire volume of air in a room )unless the room is very large. When the fan is running, the air in the room will be homogenized, not stratified. I don't see where smoke detector placement (within normal parameters) will have any effect.

I agree with ElectricAl

A paddle fan is moving the air that is already in the room, not suppling fresh air into the room like an air discharge register where with bad SD placement could prevent operation of the SD until it melts.

It is possible, IMO that the fan in some instances will cause faster operation of the SD as the smoke will travel through the space faster even though it is getting diluted at the same time.

I would hesitate to ask a your local fire guy, in this area they are notorious for arbitrary off the cuff rulings.

He may say yes you are right "no fan in rooms with smokes"

I think I remember something about placing a smokey a certain distance from a fan.
The fan moves air from bottom to top, or vice versa in winter.
As the air circulates, it will not move as much; close to the ceiling above the fan, as well as the upper and lower corners of the room.
If you wish the best placement, use a cigarette or smoke source, and see where the smoke curls in the greatest concentration at the ceiling.

The biggest reason that the fan will almost always delay the detector operation is the fact that the small volume of smoke generated when the fire starts will be diluted. If you ever take a look at how little time a smoke detector gives you to get out in a fast growing fire, you will find that even a 15 to 20 second delay could be fatal!!
Don

And this points, to me, to what is the mental hall of mirrors that can come with the technologically created safety margins.

The smoke detector is there to give us advanced warning.

The advanced warning is necessary because the occupancy is combustible.

The logic begs everything to be non combustible. . .

How do we draw the line? The paddlefan, being a creature comfort accouterment, is like the couch or the bedding or the newspaper or the cigarettes. . .it all adds to the problem that requires the technological solution of a smoke detector.