Sometimes my hardwired smoke alarm goes off for a few seconds for no apparent reason. For example I am not cooking or burning any substance. It is 3 years old and has a new battery.

Other than smoke, are there unusual gases or particles that will activate it?

The ionization type detector in question is a BRK First Alert Model No. 9120B

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    What type of smoke alarm do you have is a Photoelectric or Ionization as they both have different triggers. – iamchristos Jul 5 '13 at 9:51
  • @ChristosAmarandos it's look like it's a Ionization type detector. – ucsky Jul 8 '13 at 16:57
  • Broiling pork, or any recipes contains pork can get my smoke detector yelling fire. – Pam Feb 7 '19 at 0:49

I've seen them triggered by steam, dust, and aerosols (hairspray).

Basically, they are succeptible to small, airborne particles. Most smoke detectors activate when the particles of smoke (or other substances) "block" the detector (which is usually either alpha radiation based or optical).

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    I notice also that it's can be trigger by steam, for example when taking a shower. – ucsky Jul 5 '13 at 15:18

My hard wired smoke alarms go off for no reason once in a while. I noticed it often happens during sudden weather changes so it might be humidity. I also wonder if small insects might get into the alarms and trigger them

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    My smoke alarms just went off for no good reason at 6am. When I found the culprit alarm (red alarm memory LED was blinking) I noticed a small 5mm spider or insect crawl around on it and back inside. I'm supposing the ionization sensor detected the insect. I have Kidde model i12060A alarms. – jfritz42 Nov 3 '16 at 12:43

I've mainly found that apart from smoke that drywall (Gyprock/Plasterboard) dust can set off smoke alarms in an instance.

Also, electric power tools (like drills) can cause a spark which produces a smoke like odor setting them off in an instance.


An electrician added a ceiling fan to the same circuit of my wired smoke alarms and that would trigger the alarms for short periods of time when the fan was running, it was very intermittent and it could be days between alarms. See if there's anything "running" or being turned on and off at the time of your next alarm. You can also vacuum the detector to take care of any build up of dust, this is a good thing to do yearly anyways.

  • I don't think that anything was running but I will look this next time it's happen. – ucsky Jul 8 '13 at 16:54

Most hard wired smoke detectors made within the past 5 years also detect Carbon Monoxide- which is a good reason to get everyone out of the house until you know what's causing the problem.

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    Even if the landlord said me that it was doing CO alarm it is not written on it so I guess it's not detecting CO. I have a bunch of other device for detecting CO and so far it's didn't measure anything. – ucsky Jul 5 '13 at 19:40
  • "Most hard wired smoke detectors made within the past 5 years also detect Carbon Monoxide" - That is an INCORRECT statement. There are ionization type smoke detector/alarms, photoelectric type detector/alarms, and combination type detector/alarms that combine either ionization or photoelectric smoke sensing technology along with CO (Carbon Monoxide) detecting technology. And there are combination smoke detector/alarms that combine ionization and photoelectric smoke sensing technologies. Currently the only known detector that combines all three aspects is the Nest Protect and is rumoured to be – Wellcraft Oct 15 '18 at 22:35
  • ... dependably reliable, albeit at an elevated cost. It uses a "split-spectrum" sensor that uses a traditional infrared photo-electric sensor and a blue LED sensor, which one might refer to as a "hybrid" that provides the smoke sensing features of both photo-electric and ionization coupled with CO detection. The Nest Protect is also Wi-Fi capable, although there are still router compatibility issues. – Wellcraft Oct 15 '18 at 22:35

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