Duct Detector Testing

[MichaelGP3]

So far not yet mentioned is testing by opening a damper inspection hatch and spraying canned smoke into a hole in the sampling tube, preferably the hole that is the furthest away from the detector.

 

[gadfly56]

So far not yet mentioned is testing by opening a damper inspection hatch and spraying canned smoke into a hole in the sampling tube, preferably the hole that is the furthest away from the detector.

That could be problematic. The sampling tube is an analog integrator where you are sampling the air across the entire width of the duct. Spraying in one hole might not trigger the detector since it's sampling across all the holes in the tube. Tube spacing is 4-6", so if you have a 60" duct with 10 holes, spraying one hole is only 1/10 of the total air sampled.

 

[MichaelGP3]

I have yet to have it not trip a duct smoke detector in short order. If the red plastic cap on the end is exposed, introducing canned smoke at that location works equally well. The only scenario where this method might not work would be on the original Fenwal duct smoke detector sampling tube which hopefully have all been replaced. I don't know if there was an official recall on those, but if not there should have been; Fenwal's second release fixed the problem with better designed sampling tubes.