Attic Fire Alarm Won't Stop Going Off...Hardwired to house

10 Replies


I have woken up several times in the middle of the night to the sound of my fire alarm going off upstairs in the vacant attic. The detector is hardwired to the house so I am unsure of how to disconnect it. It will also go off randomly during the day when I am at work and my tenants have mentioned it to me.

There are clearly no signs of smoke or a fire and yet it is still going off. Anyone have a similar issue? Who do I call to fix this?


Humidity will set off a alarm. Switch out the unit with another on in the house and see what happens. 

You could also remove it and not replace it. No real reason to have one in an attic space.

@Thomas S. I would like to have it removed if possible, I am not sure why it is up there but now that @Matt Bacenet brings up the possibility of it also being a CO makes sense.

I will double check this when I am home later today.

If I suspected it to be Carbon Monoxide, would I need to reach out to the Fire Department?

If it also has a CO detector you could be getting CO (from furnaces or HW tanks) back drafted into the attic from the chimney. We found that you don't need much of a 'crack' or spall in the inside of the chimney to create such. Also some old attics may have had an old heater chimney opening that has since been abandoned that may also allow the CO backdrafting. 

Insect or fine dust debris etc can also cause the sensor to activate. If you know how to diagnose that clean it or better yet replace it. Also make sure the alarm is not near a hot air vent or cold air return as fine dust can coat the sensor. High humidity can also activate an ionization sensor alarm so any venting of showers/dryers etc into the attic area (& we see a lot of those) can cause a false alarm. 

I would also check the integrity of the hot wire connections into the suspect alarm as these have been known to generate false alarms.

Personally I'd be reluctant to disconnect it until you establish the cause or just have it replaced if its older than 5 years.

@Steve DellaPelle if it is a CO alarm and you suspect a CO leak, I would call the gas company and have them send someone out asap. more than likely, they will try to find the leak and do a temporary fix until a GC can come out and permanently fix the issue. CO will kill you slowly and it doesn't have a smell. I would make sure when your up there you open up all the windows and don't stay up there long. its best to have someone by the door just in case you pass out, they can pull your body out. I know it sounds ridiculous but that's how CO works. you will get sleepy and just pass out. after a while of your body not getting O2, you will die. if you want to check, you can get a hand held CO detector from lowes or home depot and take it up there with you.  

I'll start by saying that I'm assuming you have smoke and co2 detectors in your home and rental unit and that they're not going off. 

If I had to guess, I'd bet its the device.  Try changing it out first and see if that doesn't address the problem.   Those sensors on the co2 units are pretty sensitive. A little dust in there and those things will go off sporadically all the time. The wired ones are way worse than the individual ones. Not sure why that is exactly, but it is.

My electrician once told me that it helps to have all the same brand on the detectors if they're wired. Makes no sense to me but it fixed the problem I was having at one house so there may be something to that too.

@Steve DellaPelle It's too cold in your attic (assuming it is unheated space?). I'm not sure what the temp rating is on smoke detectors but I see them going off all the time in vacant unheated houses during the winter when the power is left on and the heating system is shut down.

@Steve DellaPelle   Replace it. Smoke detectors do go bad. They are cheap and you can likely find one with the same exact plug. The issues is the bad sensor will cause the other detectors to start sounding since they are hardwired (the third wire going to the hardwired smoke detectors is used to signal all connected detectors to go off).  On of my houses was built in 2010, and I have had 2-3 detectors go bad.  Given they cost about $10-15, just buy new ones and throw the old one out.

If it has CO then they typically have a lifespan of about 7 years.  I had an expense wireless Honeywell model that tied into the ADT alarm system that went out.  Replace with a combo fire and co unit.  I would keep a unit in the attic as it sounds like its a walkable attic.  Not putting on back may create an open circuit and will trigger the other units to go off.  

Thanks for the responses give a little more details...this attic is an unfinished area that used to be 2 is now vacant and does not have any heat.

There is another alarm/detector on the other side of the attic (this is a 4-unit building, 2 units on left side and 2 units on right side) and that one does not go off. This is the only one going off it is not setting off any other ones in the building.

I recently purchased this house August 2017 and I am pretty sure the alarms/detectors are new and in working condition as this was inspected by the fire department before closing.

With all of that said and with the answers above, I believe this is a false alarm of sorts and may just need to be vaccumed and dusted off.