I had this problem in my own home last night. Husband is out of town on business. Smoke alarms all went off around 2 AM. I grabbed the dog and my keys and got her in the car and then alarms stopped. I went back in and checked the house and everything seemed fine. One smoke alarm in the basement had a red light instead of a green light so I switched out the battery. But the battery should not cause the whole house to ring, right? I should just get a chrip for that. The dog and I slept in the car last night because I was nervous about coming back into the house. But all seems OK this morning. Any idea what this might have been? We did have a lot of rain last night so I guess it could be humidity, but that’s never happened before. Probably isn’t dust, as my house is pretty clean. Yikes. Thanks, I know you all are a pretty smart bunch. --67.172.xxx.xxx

All for smoke only or any for carbon monoxide? Do you have gas coming in the house? Any hardwired in? --99.203.xx.xxx

We have propane. We have a carbon monoxide detector wired into the basement and a separate plug-in Carbon monoxide detector upstairs next to the fireplace. All of the smoke alarms except the standalone CO2 detector are hard wired together. Only appliance easy and propane this time of year is hot water heater. --67.172.xxx.xxx

I meant that the only appliance using propane is the hot water heater. Upstairs plug-in CO2 detector did not go off. If I had a CO2 problem in the basement, would the alarm continue to sound? Thanks. --67.172.xxx.xxx

Maybe I should take the standalone plug-in CO2 detector into the basement and just make sure everything is OK down there. --67.172.xxx.xxx

All quiet. --67.172.xxx.xxx

well, if it is hardwired, then obviously it triggered the signal (red wire) to send to everyone of them.. I would just replace that one blinking red --108.34.xxx.xx

I would most likely replace the one that had the blinking red light. As long as you can replace it with the same brand & model # it should be fine. --96.237.xx.xx

A spider can set them off. Also how old are they? One that “goes bad” can trigger them. Vacuum all of them, change batteries, and consider replacing if they are 7 years old. All the ones at my rentals were around 7 years old and 1 in each unit started failing causing problems. No issues since replaced. --24.61.xxx.xx

I've had several instances of a faulty detector causing an alarm like this. In these instances I replaced all detectors. An electrician should be able to troubleshoot this for you --70.178.x.xx

You are wise to follow up and figure out why. I wouldn't like being woke up like that either --99.203.xx.xxx

How old are they? Smoke alarms are supposed to be replaced every 10 years. Mine went off at 3:00 am once. Great time to hear that noise right? Mine were about 12 years old so I replaced them. I didn't find any bugs or dirt inside the old ones when I took them down. --131.201.xxx.xx

Electrician coming tomorrow to replace all of our house ones. I can only get the talking ones now at HD and don’t want those. And some of the connections need replacing. --70.16.xxx.xxx

Heavy humidity can set off a smoke detector. --174.192.xx.xxx

Since they are all wired together they all go off. I had to do that at my fourplexes for the inspection fire code. Maybe a bug got into the one with the red light on it and set it off or the battery backup is bad and it let you know. You did the right thing to get the dog and get out. --173.61.xxx.xx

Thanks everyone! The smoke detectors in the basement are only a year old since we remodeled last year. They still had Original kiddie batteries in them. So I guess it must’ve been the humidity or a spider or year old batteries going bad. I just now woke up after being up all night in the car. Yuck. But all quiet since then. Thank you so much everyone! --67.172.xxx.xxx

How old are they? Most expire after 10 years, even the hardwired 1’s The hardwired 1’s in my house did that, first I just replaced the 1 that I thought it was, it kept happening. So I just bought a pack of 6 online and replaced them all. Hasn’t happened since. When they get old dust inside of them causes them to act screwy. --174.199.xx.xxx

Then wait and see what happens. If that unit goes off in another area, you know it's the unit. If the basement unit triggers then maybe it's picking something up. You could replace smoke for heat detector in basement if the test fails and there's no fire. Bring a flashlight with you when it goes off so you can see if there's any smoke in the air. --108.69.xxx.xxx

--73.102.xxx.xxx

No need for an electrician if they all went into alarm - she/he would check wiring continuity in the walls but this proved that is fine, most likely is a photo type detector which is a common generator of false alarms because only one field of light to be broken, use ionization ones to prevent the false alarms, they cost a little more and are about 3-5 seconds slower to alarm but it is real when they go noisy. I use BK 9120b in my places. --76.188.xxx.xx

Thanks everyone! Turns out we had some sort of brown out or a power surge or something in the neighborhood. Neighbors reporting GFI’s popping. --67.172.xxx.xxx

We have this problem in one property near the power station. They are hard wired. In the summer when usage is high across town they “ switch over” the power grids at night ( usually at about 2 a.m). Just about every year this causes one of the alarms to go nuts. We keep a supply of them and just switch out to a new one when that happens. Spiders have done it too. Easier to replace than to try to troubleshoot. --71.10.xxx.xxx