Security & Fire Protection Systems/BRK 4120B smoke detector


Melody wrote at 2006-06-30 18:20:48
I'm not the original poster but I have the exact same problem.  And my house is new.  It was built 3 years ago - for us.  Last night (or rather this morning at 2am) this problem happened for at least the 3rd time.  The most recent previous time was only 2 weeks ago.  The time before that was 6 months earlier.  Each time all smoke alarms were inspected (no dust or dirt of any kind was found) and all batteries replaced.  (It happened some time prior to 2weeks, 6 months but I don't recall exactly when.)

I called Duracell today to see if I had gotten hold of some really old batteries from the store.  Duracell told me this is a known problem.  Duracell said that there is a flaw in the way the battery engages and the flaw can cause the battery to draw house current.  Duracell said this frequently happens around 3am.  Duracell said that some customers have reported hearing a loud popping noise, almost like a gunshot.  (I mention Duracell so often to make it clear that this is the information I got from Duracell.)

However, when I (or rather my husband) called BRK, the story was different.  BRK also said this seems to happen at 3am.  However BRK says it has nothing to do with the house current.  BRK suggests thoroughly cleaning the units - including spraying them out with pressurized air.  They then say to put the units back up but do Not connect to house power.  Then if one of the units goes off, we'll know just which one is defective - if any.

So, the smoke alarms that are wired to my house by law, I must now disconnect and have use only battery so that we can figure out which of the defective units is defective.

My personal opinion is that there is a design flaw in the units as Duracell indicated and that BRK is hoping they don't have to replace all of them.

Melody wrote at 2006-06-30 18:26:13
I just found this news article.  My smoke alarm units were manufactured after 2000 so imho there is still a problem with Duracell in these units.

Nancy wrote at 2006-07-14 04:35:07
Our BRK 4120B manufactured Jan 24, 2003 alarms worked great for the first year in our new home, when the first one chirped, I replaced all 5 batteries with Eveready, and they worked fine after that with the exception of a period when one would set all off with a test alarm sound.  They would go off in the middle of the night, and before I could see which one was alarming, they would reset.  They quit the false alarm after a couple of nights until this year.  I've replaced all five batteries, but they still go off as before, mostly in the middle of the night, but have done it now during the day.  I did replace them with Duracell (before I read this site), so I'm definatly buying Eveready again tomorrow, but I'm wondering if I should just replace them with the newer model BRK has in place of this model.

Kathy B wrote at 2006-10-04 11:54:17
I am having the same problem and found that this model not only has been discontinued, but has had dangerous problems with batteries exploding if you don't put the "right" battery in.  There is a consumer alert out on this item that states that you can only use Eveready batteries numbered 1222 or 522.  Because of the design of the battery cavity, the smoke detector can cause other batteries to overheat and potentially explode.  I'm still trying to identify the problem with my detectors going off.  The builder of my home put these detectors in 2 years ago after the alert was issued and did not inform us.

Kathy B wrote at 2006-10-04 12:01:59
This is outrageous.  BRK knows they have a problem.  They are waiting for us to all replace our alarms....with their newer (hopefully improved) products so they don't have to pay to replace them.  This is just like car recalls that occur years after you've gotten rid of the vehicle and people have died because of a manufacturer's defect.  What are they waiting for and why are they denying the problem?  My family doesn't even respond to the smoke alarms going off anymore.  We've been awakened night after night at 2, 3, and 5am.  The kids have learned to ignore the alarm.  If we really had a fire.......I don't know what would happen.

SHAME on First Alert and BRK!!!!!!!!!

Jason P wrote at 2007-06-18 03:15:40
Ours did this the other night.  They would keep testing and resetting all through the night.  Angry and sleep depriven with a crying two year old and a distraught pregnant wife, I removed them from the wall and disconnected the batteries!  I will purchase others, of a different brand, and rewire my house, if necessary.  I will also join any class action lawsuit if someone has the means to start one!  I can't believe that UL signed off on this one... oh wait yes I can, UL is a sham.  I have interfaced with many of their auditors personally and they stress everything that is unimportant and whimsical and completely brush under the rug things like this.  I will check back in a little while to see if people are willing to start a class action lawsuit.  I will not tolerate this type of irresponsibility when it comes to the safety and sanity of my family.  This is utterly unacceptable.

Keith F wrote at 2007-07-20 02:31:37
I have had problems with these alarms for over 7 years.  Until tonight I had never come across any reports of problems with this detector online. My house was built in 1999 and shortly after moving in the detectors went off int he middle of the night.  Since then we have dealt with the alrms going off randonly every 6-12 months int he middle of the night.  Last nightm they went off twice, once at 1am and then again at 3am.  I had been using Energizer batteries model#522 and found the batteries in two of my units swollen tonight.  I changed the batteries and cleaned the units tonight hoping I can kae it to the weekend without a issue and then replace all 7 of the detectors in my house.  Call BRK today proved usless.  I am planning to ship them the smashed pieces of my 7 detectors along with the swollen and exploded batteries that they recommend be used int he detector.

SteveM in Des Moines wrote at 2007-08-09 02:50:15
I've had three batteries blow in the last month, all Duracell. Now I know "why". My two most troublesome units BRK Electronics Model 4120B were both manufactured 1999 SEP 01. The back of the unit and a sticker in the battery drawer it recommends Duracell MN1604, which is the brand/model of the battery that exploded tonight.

Even when the batteries don't blow up, these detectors ate batteries like crazy. I've taken both units out of service. I'm more scared of starting a fire with these than detecting one.

I agree with the others. This is a dangerous design flaw and BRK needs to make this right. Sign me up for the class action law suit. Don't throw away your batteries. Keep the evidence.

I think it is time to get the press involved and or our State Attorney Generals. Iowa's State Attorney General just won against Microsoft.

Susan N wrote at 2007-09-24 23:34:53
A couple of weeks ago we experienced our first incident and the detector went off in the middle of the night.  When we opened it to replace the battery it had exploded.  We replaced it with a Duracell and called it a night.  A few nights later, it went off again and not only did it scare us to death, our 5 year old was traumatized.  When we took the detector down we found yet another exploded battery.  Today I just came home from work and found a dectector in our spare room chirping.  When I opened it, yet another exploded Duracell.  I decided to google what could cause a battery to explode in a smoke detector and found this site.  When reading it I was shocked to see that this was the exact same smoke dectector that we have been having go bad.  We will be replacing with another type detector tonight!

Gordon wrote at 2007-12-30 19:00:14
I have the same problem.  My alarms are Kidde 1276, all connected together and all using AC/battery.  These are 3-1/2 years old. The original batteries lasted over three years.  When the first battery became discharged and the 1276 began chirping, I replaced all the batteries with Duracell MN1604.  This was a month ago.  Since then, I've been awakened four times -- all about 3am -- and have seen two burst MN1604.

Andy wrote at 2008-01-26 17:46:08
We have been dealing with this same issue. What troubles me is that we have the 4120B, manufactured in 2004. The only advisories we have seen are for models made before 2000.

We have had four instances of the alarms going off. The Duracell batteries I have removed were slightly bulged.

The bad part is that our alarms are wired, and there is supposed to be an indicator stay on so you can tell which unit was the first to go off. But that isn't happening.

What's weird to us is that this has only occurred on cold, windy days. I wonder if there may be some relation to a change in air pressure or something, too.

peejmeister wrote at 2008-02-22 14:47:26
I had a very similar problem.  10 chained together, last few nights they would all go off sporadically.  I happen to notice the one that triggered them (flashing red LED).  Replacing all the batteries had no effect.  Turns out, a small spider took up housing in the offending unit and apparently was triggering the alarm (spiders are active mostly at night?).  I had to take the cover off the unit releasing the 3 'stirrup' latches.  Cleared out the spider and his web and viola, no more false alarms.  No more screaming, panicky kids!

Rex wrote at 2008-05-17 06:14:22
The same thing has happened twice with Duracell 9 volt batteries in

two of our smoke detectors. The most recent incident occurred just two

days ago. My wife told me she heard two loud popping noises and

smelled something burning. She determined that it was coming from the

smoke detector which started beeping.

The codes on the bottom of the most recent failed battery is G626 G107

with an expiration of Mar 2011.

I'm not sure if this is a Duracell issue or if it is an issue with our

smoke detector. However, we have used other brands of batteries in the

past without any issues. The brand of smoke detectors that was

installed with our home is called BRK Electronics.

Mike wrote at 2008-08-07 07:55:09
It is 3:30 AM and for the third time in as many weeks our smoke alarm has gone off in the middle of the night. "Googling" our model number, we are shocked to learn that we have the defective BRK model 4120B. We will be purchasing battery operated alarms in the morning (should I say when the sun comes up).  We appreciate this forum as well as similar ones where we have just learned of this very dangerous condition.

P.S.:  Five of our eight detectors had Duracell replacement batteries in them!

Carl Farrar wrote at 2009-06-21 23:34:27
I've just had my experience with random sounding of the alarms for the last two nights.  After reading some of the other peoples experiences, I decided that spiders in the units was probably my problem.  I took them all down (nine, connected together) and blew them out with compressed air.  Three of the nine had evidence of spiders.  One of those three had a small live spider in it.  The second of the three had two dead spiders and a lot of web.  The third just had some old web and the remnants of old spiders.  It's been thirty minutes now, without an alarm.  I hope we make it through the night without an unnecessary alarm.

Tired and Grumpy wrote at 2009-07-20 09:07:26
Well, In a shameful way, I am glad to hear I am not the only one with this F'n problem.  What a piece of crap.  I have 8 of these pieces of crap and they are all going off in the middle of the night.  I am unplugging all of them and will replace them with whatever brand I can by from Walmart, Lowes, or Home Depot tomorrow.  Here it is, 3am and I can not sleep because these things keep going off.   Thanks for posting everyone because I will admit, I was not sure if I actually had a problem in the house or if there was some sort of gas leak being detected by these crappy things as well.  

FreddyS wrote at 2009-07-28 15:06:07
Yes, I too have a 4120B that chirps in the night. A year ago when it first happened I replaced all the batteries. A few months later it happened again. I figured I got a bad battery but there is no easy way to tell which of the 10 detectors is the problem. two months ago I realized that one detector had a bulging Duracell. I replaced the battery and moved this detector to a different location as a test. The same detector went off last night with another bulging Duracell. Just today I found the info about using Eveready and the info on this site. I guess I will try Eveready before I replace the detectors. Is the BRK 9120 a fix for this problem.

DeeR wrote at 2009-11-17 01:40:37
Yes, we have been dealing with this problem for years.  We keep hoping that they will recall since we have several in our home.  It is ALWAYS in the MIDDLE OF THE NIGHT!!!!!!!!  We are Sooooooooooooooo tired today from last night and soooooooooooo tired of dealing with these pieces of crap!  HELP!

Jen wrote at 2009-11-26 04:27:14


Wow!  We have been dealing with our alarm going off all week.  After returning from Hawaii this is what we came home too.  Went to WalMart to purchase new batteries at 11pm, they went off again until 3am.  The next day it chirped twice but when we went to bed at 10pm they went off until 3am when I couldn't take it anymore.  My husband took off all the batteries and they still went off.  The next night at 11:30pm he disconnected the power to them and took them down, we finally got to sleep.  Went shopping for new detectors tonight and couldn't find them, thought I'd get them on line.  Was I ever shocked to find this website and read all the problems with this model.  We too will replace with a different model.

Kate and Jim wrote at 2010-05-27 15:49:38
At around 3pm yesterday, very loud bang (like a gun) and the smoke detector went off. The people on a science forum gave me this link, 9v battery had exploded...yep a Duracell. We just bought this house, the previous owners had remodeled around 2003 and 2005. Various things have been wrong so this is added to the list.  

jimdandy wrote at 2010-06-26 09:51:49
Let me first say my house was built Jan 2001, and it is directly next many High power lines (within 300').  The first incident just occurred few weeks ago. I had one smoke alarm start chirping in the middle  of the day, then very quickly two more began chirping. I opened the first alarm and was surprised to see the 2 week old 9V Duracell Coppertop severely ruptured.  But then I was shocked when I saw all 3 were ruptured. "Ok that's a first."  I thought as I began to replace the batteries.  As I reached up to the alarm, with the New-new 9v Duracell in my right hand,at just about face level, the battery exploded. The sound, feel, and flash all resembled a large firecracker. The force of the battery rupture completely removed both ends of battery. Needless to say, it popped right at eye/ear level.  Which was still about 2 or 3 feet from the smoke alarms. Which are all mounted on the ceiling.  I did not feel any electric surge at any time during the first incident. I say first because I got a second,"new", Duracell, and it also exploded as it was moved to within a distance of about 24" of each chirping alarm.  Yep 3 initially ruptured, and then I repeated the event six more times on all 3 alarms. There seems to be very high surges of power with the hardwired alarms. While possibly also receiving bleed over from the powerlines above me.

David Butler wrote at 2010-06-27 05:20:59
Some of the comments posted here appear to describe 'normal' false alarms (must kill power to stop alarm). That can happen with any brand (dust, insects, etc). Other comments used the word chirp, indicating a low battery alert. That would also be normal. Unfortunately, when multiple units are interconnected, this model provides no indication which unit caused low-battery alert. In any case, it's best to replace all batteries at the same time.

Note: It is important to verify that the red LED flashes every minute or so on all units. If no flash, then the battery is either stone dead or it's not making contact with one or both terminals. This would be a quality control defect or design flaw, and would warrant a free replacement.

Aside from the battery exploding issue, which presumably was resolved with units made after 2000, I was unaware the 4120 had any other issues. That is, until tonight. The alarm pattern I experienced is not documented in the manual. This evening my 4120B units sounded 3 beeps, pause, then 2 beeps. This repeated at random intervals for about an hour. Even though this is not a low-battery indication, I replaced all the batteries. Since my unit was manufactured in 2003, I used Duracell, which is what l had on hand. I'll post again if this undocumented alarm recurs, or if a battery explodes =:-o

Here's a summary of the alarm codes for models 4120B, 4120SB, SA4120B:

* A real or false alarm (e.g., dust, smoke, insects) will trigger a constant alarm until reset. The red LED on offending unit will flash quickly.

* Pressing test button will cause 3 beeps, pause, then 3 beeps.

* The low-battery alert is a brief chirp every minute or so.

David Butler wrote at 2010-06-29 15:29:07

A quick update on my previous comment from 6/27...

As expected, changing the batteries made no difference. I've continued to get nuisance alarms. However, I need to make a correction: Contrary to the documentation, pressing test button causes 3 beeps, pause then 2 beeps -- that's exactly the pattern of the nuisance alarms. This makes me wonder if these units are designed to provide an initial non-continuous alarm as a precursor to a real alarm. That way, if it's a false alarm due to dust or insects, a power-off reset would not be required. As a seasoned design engineer, that would be my guess. If true, shame on BRK for omitting this little detail from the User Manual.

In the meantime, I disabled all five detectors and blew out the dust with compressed air (a vacuum cleaner is useless; it can't reach the internals). You can buy a can of compressed air at Radio Shack. I decided to re-install one at the time, letting each one operate a couple of days before adding the next. That way, I'll discover if one of my detectors is actually defective.

BTW, with all due respect to Mr. Jimdandy, his testimonial describing two separate incidents of unconnected batteries exploding in his hand is simply not credible, and is certainly supported in physics. If it happened one time, I would chalk it up to some sort of bizarre coincidence - after all, batteries can be defective. But eight in a row? I don't think so. And that nearby high-voltage power line is a red herring. Although there is some evidence that long term exposure to strong EMFs may have health consequences, the current levels induced by power transmission lines are FAR too low to fry a battery. And the EM field around a smoke detector is virtually non-existent.

lawendt wrote at 2010-07-24 18:41:29
We had 12 of the BRK 4120B installed in our house during renovation in 2000.   They were all replaced by BRK in about 2006 due to the same issues described above.   Every month or so, they just start to go off.  The only way I seem to be able to get them all to work for any length of time without false alarms is to replace all the batteries at once.   Even then, it may not solve the problem.   

I'm looking for a compatible replacement that can use the same wiring connector so I don't have to mess with the junction box if possible.   Any suggestions?

Jason Cole wrote at 2010-08-17 06:37:08
Our home was built in 2004 with the BRK 4120B Smoke alarms.  Now in 2010, the alarms are all going off the the three continuous beeps at 11pm Aug 16(keeps going off every 15 minutes or so).  I started disconnecting one at a time.  They all kept going until they were all disconnected.  I've cleaned them with the can air, but that isn't helping and I'm using a Rayovac 9V battery that the manual says is supported.  I'm not sure what to do next accept replace them all with different alarms.

Bob wrote at 2010-09-05 10:45:08
Not going into a lot of detail here but my story is about the same as others with false alarms. My house is 2 years old and the alarms are Kidde model i12060. False alarms are not rare but after changing all the batteries i still had the same problem. And i did use canned air to blow them out. The reason i found this site is that I've had two duracell 9 volt batteries explode after removing them. Both were laying on my desk and this happened days apart. I was looking up why batteries would explode? Both had the bottom fly open and a blue power fly out and and a few parts hanging out.

BRK Hater wrote at 2011-01-10 04:13:35
I have had same experiance as everyone above over the past 5 years. But has anyone had their green light not light at all. I even swapped locations and detectors around the house and still just THAT ONE detector does not light green. Test function works fine.

Does anyone know where to get replacement? that model does not exist on BRK website (PRODUCTS PAGE) nor in their electronic electronic catalog. But I do find spec sheet and manual for 4120B.

Stacey G. wrote at 2011-01-23 18:33:08
As I write this my husband is replacing all 6 BRK 4120B(manufactured in 2003)smoke detectors in our home with another brand.  These units were installed when our home was constructed in 2004 and have been a source of frustration ever since.  Randomly they will all go off at 3am as well as all other hours of the night. This most recently happened last night, the batteries are new, Ever-Ready, installed into cleaned units, one week ago.  My fear, if there were an actual fire, we'd die! While building a fire in our fireplace this past week quite a bit of smoke escaped and I could see it rolling across the ceiling RIGHT OVER THE SMOKE DETECTOR, IT DID NOT GO OFF!  If you have these units, get rid of them.  I am going to look into filing a "class action suit" and will post my findings.  

Stacii wrote at 2011-02-08 04:11:39
So, I am the nervous type anyway so when those smoke alarms go off in the night I about jump out of my skin - and it's ALWAYS at night.  I am not sure what everyone means by normal false alarms, but we don't have chirping here - it's full on "FIRE" alarms.  They go about 15 seconds then stop. Then 30 - 60 minutes later, again.  Then an hour later again.  This happens about once each year, and it happened last night.  It makes you want to disconnect the entire system. After last nights second alarm I sprayed all of them with compressed air, which made them go off again for a moment.  Then it stopped.  After reading your posts I actually pulled them apart and sprayed the inside with compressed air this evening in preparation of another night.  Got seriously dusted on one of them, and saw spider webs.  On another the hard wire pulled out, so it may have been loose.  I ran out of air, but hope I did enough.  Batteries were replaced 30 days ago and are not swollen, so that shouldn't be the problem.  Wish me luck. I will post tomorrow with an update.

BrianH58 wrote at 2011-03-28 19:27:51
I have 6 of the 4120B units installed in 2003 or 2004.  They have been going off periodically for the last couple weeks and I can't discern which is initiating the problem. Red LED's flashing on all of them (I think?) I vacuumed and replaced all batteries, to no avail.  Last night I just took them all down... it won't do me any good to kill myself falling off the ladder on the balcony trying to take a screaming alarm down in the middle of the night:).  I think I'll junk them and put in some battery operated non-interconnected units.

Jason Bennett wrote at 2011-04-13 20:26:20
Happy to see I'm not going insane,although very tired from my 6 BRK 4120B smoke detectors going the last two nights.I built my house in 2003 and started having this problem about a year later. They alarm a couple times a year and it's always between midnight and 4am. They only alarm long enough to scare my family to death,not long enough to see which one of the interconnected units triggered the alarm.New batteries typically solved the problem before, but not last night.I disconnected two detectors last night and the alarm stopped.

Found this site while looking for BRK Electronics site.I'm going to call BRK to see if they have anything profound to say about the junk they sold. It will probably come down to me buying 6 new smoke detectors of another brand of course. Wonder if BRK will reimburse?

JT wrote at 2011-06-05 05:26:56
This blows my mind there are so many people are having this problem with BRK 4120B.

We have seven units, interconnected. Yes, 3:30 AM they decide to go off. What on earth is up with the time of this?

Actual alarm. Three sirens pause and another three sirens. Two cycles then nothing. Maybe fifteen minutes later the same thing.

About five times this happens then nothing further. No red LEDs! No latch alarm!

Batteries all good. Units properly located. All units cleaned.

ADT is monitoring me and they swear the are not reading any alarms. WTF!!!

Socaloha wrote at 2011-06-29 08:53:21
Hello all - it's about 1:45 A.M. PST and here I am.  I'm glad I found this site... My house was built in 1998 and has 6 of these alarms.  Based upon the comments here, I guess I'm somewhat lucky to not have had such problems with the alarms.  However, for the last 2 nights, all alarms go off for about 2-4 cycles and then stop.  2 nights ago they went off in this intermittent cycle for about 30 minutes and then stopped.  During the day it happened twice 7 hours apart.  Then yesterday nothing for 10 hours.  But now they go off every 15- 30 minutes.  I replaced all the batteries yesterday during the 10 hour silence and thought I was good to go.  Apparently not.  Since it's been 13 years, it seems I need to replace them as they are out of warranty.

Rich wrote at 2011-07-03 10:18:09
Well, I guess I am the newest member of the club. Started @ 2:30 AM MDT. After walking the house a few times to make sure there wasn't something going on, still getting false alarms @ 4:15 AM. Is the date on the sticker the creation date? If so, mine were made in 2002, supposedly after their fix.

Hopefully I can get some rest tonight and get them replaced tomorrow. From this posting, it appears that once it starts, there is no end in sight.

James TX wrote at 2011-07-12 02:27:16
OMG! I have the same problem. This is insane. It should be a recall!

Don in Ohio wrote at 2011-07-21 10:52:40
I guess it is my turn to join this exclusive club, Mine are acting very much like what everyone else here is describing with teh false alerts.  I did find where the BRK 9120B is a direct replacement for the 4120B but, like many, I see no good reason to buy another from the same company and therefore "reward" them for ignoring an obvious issue.  

Derek wrote at 2011-08-07 04:27:39
I have the 4120B's about 10 wired in my house.  They chirp.  Replaced batteries.  Did the discharge thing.  They still chirp.

I hate smoke detectors.  I think I will have to replace with battery operated ones.  Not too interested in going with hard wired anymore.  It's a pain, because the hole in the ceiling chirps even with all the detectors removed.

Melissa wrote at 2011-08-19 04:34:16
We have had the same issues in the past until we pulled down 3 of the units from our 2nd floor about a year ago. All the ones on the main floor and basement were fine. When we got home tonight we could here a chirping from the casing of one that has been down since last year. We replaced all batteries in all the others and blew them out with compressed air. That one was still chirping. We even killed them at the circuit breaker and this damn thing still chirped. So now we have killed the hardwiring at the breaker and pulled them all down. Going to check with an electrition and then probably go buy regular battery operated ones. This is the pits!

Frustrated in PA wrote at 2011-08-28 06:48:15
One question- why can't the false alarms occur during normal waking hours?  Always at night based on our experience and from the comments of those before us.  We have the several of the 4012B models and seemed to have joined this exclusive club against our will. We will try changing batteries and cleaning out the dust.  

I've had enough! wrote at 2011-10-13 20:48:38
amazed by the number of people experiencing this issue.  went online and found more answers: first disconnect from  both hardwire and battery, hold test button down for 20 secs to clear memory, blow unit out with compressed air and reinstall...

another key factor: the US Fire Admin recommends replacing the whole unit after 8-10 years on all unit was 12 years old...guess it's time to replace the things... won't be doing it with the BRK model though...

kendra wrote at 2011-11-02 20:46:05
Hello my fellow pissed off BRK 4120B smoke detector owners.

The past 2 nites in a row they have went off. Replaced the batteries the first time & thought that should fix it-DIDN'T! Nothing like waking up at 330am scared half out of your wits trying to get the kids out of the house coz there is a fire-wait, no there isn't! $500-$800 fee for fire truck call, do you think BRK would pay it? Glad I found this site! Please let me know if/when there is a class action law suit-I WILL JOIN! Off to buy new system that is not related to BRK!  

Matchbox Twenty 3 am wrote at 2011-11-07 09:24:55
I just joined the club.  What's special about 2-3 am?  Any suggestions on replacements other than BRK that are easy?

Edward P. wrote at 2011-12-03 03:32:58
This happened to my family 2 years ago. We haven't had time to replace the fire alarms so our house has been unprotected for a few years. We're calling over there tomorrow and if the don't replace all of our alarms we're taking legal action because this is just ridiculous. Justice needs to be served.  

Angry He Hulk wrote at 2011-12-07 04:28:21
I have the wonderful experience of dealing with these pos BRK 4120 B. I hate these, I have smashed them one by one over the years and replaced them with different lowes or home depot brand. I had one malfunction tonight and tried to take it out and it kept chirping, He Hulk smashed it into the tile floor. This eliminates the problem of the BRK 4120B. When the snow outside set the other one off the other night and the ladder was buried under a foot of snow my handy BRK Smashing hammer nicely reaches the extra 3 feet to the ceiling and comes to the aide of He Hulk. I took the unit to the garage and my anvil and showed it that He Hulk was truly mad. I hate these things. Do not buy BRK products. If you want to have your blood pressure raised and lose sleep, then these POS units are for You. He Hulk has decided to go visit the one working unit in the house now and take proactive measures against the Sleep eliminator BRK 4120B and do some soul gratifying SMASHING!

DisgustedAlaskan wrote at 2012-01-07 19:13:20
Sigh. I've been dealing with increasing problems with the dag-nabbed BRK 4120 over the past couple of years. The alarms were installed in late 2001 or January 2002 as part of new construction. Seems to always start in the middle of the night (about 2:07 am this morning and continuing on from there). Always in the winter, which is heating season (forced air). At least no exploded or damaged batteries (yet). Last replaced the batteries in Oct. 2011 ant my tester says the four I have removed all have sufficient juice. I've not done anything yet with the 5th because it's up in the cathedral ceiling and I hate getting up on the extension ladder and leaning backwards and trying to get that *&*&* plastic door open and closed. I expect before the weekend is over I will be moving furniture and removing that battery, too.

All five are also hardwired and interconnected. So here I sit, with no power in my living room, dining room, kitchen ceiling lights or garbage disposal because I had to throw the circuit breaker. Not fun stringing extension cords around to run the floor lamps and other devices. But doing so is necessary since we only have about 6 hrs of daylight this time of year.

Plan to call an electrician Monday to replace them and check out the system. I would also love to get them onto their own circuit but probably won't be able to do so at this time. Perhaps by Friday I will be able to turn the circuit breaker back on.

DisgustedAlaskan wrote at 2012-01-07 19:13:49
Sigh. I've been dealing with increasing problems with the dag-nabbed BRK 4120 over the past couple of years. The alarms were installed in late 2001 or January 2002 as part of new construction. Seems to always start in the middle of the night (about 2:07 am this morning and continuing on from there). Always in the winter, which is heating season (forced air). At least no exploded or damaged batteries (yet). Last replaced the batteries in Oct. 2011 ant my tester says the four I have removed all have sufficient juice. I've not done anything yet with the 5th because it's up in the cathedral ceiling and I hate getting up on the extension ladder and leaning backwards and trying to get that *&*&* plastic door open and closed. I expect before the weekend is over I will be moving furniture and removing that battery, too.

All five are also hardwired and interconnected. So here I sit, with no power in my living room, dining room, kitchen ceiling lights or garbage disposal because I had to throw the circuit breaker. Not fun stringing extension cords around to run the floor lamps and other devices. But doing so is necessary since we only have about 6 hrs of daylight this time of year.

Plan to call an electrician Monday to replace them and check out the system. I would also love to get them onto their own circuit but probably won't be able to do so at this time. Perhaps by Friday I will be able to turn the circuit breaker back on.

Kim wrote at 2012-01-13 01:02:53
We have had the same problems for years! Ours usually go off near 4 am, but last night it was midnight, and then again a few minutes later. It scares the entire household and my blood pressure is so high I can't go back to sleep! For us it is usually in the summer, but we have more air movement in the summer since we are in Houston. Ours were manufactured in May 2003. Does anybody know an attorney who can take up our cause?!

Asad wrote at 2012-01-26 15:52:13
I've had this problem intermittently over the past four years, although I've been in this house now for seven, and it was built in 2002-03 (the 4120Bs were manufactured in April 2002).

The alarms went off last night starting at 3am, 3:45, 4:15, 5:30, 6:45, 7:15, but have had longer intervals during the day. I'm still not sure why this problem only occurs at night.

Thankfully I haven't had any Duracell batteries (which is what I've used in all 9 of my detectors) explode *yet* but I'm going to replace them all with evereadys today.

I'm going to disconnect them from each other and see which one is the problem detector, and replace it. I find it hard to believe that all 9 of them are defective. We'll see.

3am alarm wrote at 2012-02-08 04:14:53
We jsut experienced the same problem.  3 a.m we have the alarms blaring.  We rush through the house to see if there is a fire or smoke and nothing was seen.  Try to go back to sleep a few minutes later and the alarms sound again.  This went on every 15 minutes or so until well after 5 a.m.  We are just thankful there was no fire or smoke.  Immediately replaced all 7 smoke alarms in the house with Kidde brand.  Have not had any problems yet.  When I unhooked the BRK from the wires they continued to sound an alarm and continued even when the batteries were removed.  Ended up having to smash them to silence them.  If this happens to you just replace them and do not go through the effort of trying to determine which one is faulty.

Red Eyed in the Midwest wrote at 2012-07-29 12:13:37
Just like everyone else around 3:00am off go all of our 9 alarms. Then trough out the day if keeps going of. We changed several batteries to no avail. To make things worse we had several family members over for dinner that day. Finally at around 9:30pm our nieces boy friend figures out which unit is going off first, removes it and the damn things finally stop. We will throw out every unit as soon as we can.

Red Eyes wrote at 2012-08-18 16:07:21
Same problem here.  It happened when we first moved into our house, which had about BRK 4120B.  It also happened in the middle of the night and prompted hysterical screaming kids.  The first time I ran out to the store at midnight to get all new batteries.  That solved the issue for a while, but predictably occurred again about 6 months later.  I'm finally at wits end and replacing them all.  I'm thinking I'll replace with Kidde models since I can't support BRK/First Alert.  Just make sure the model you select has a compatible connector, but it seems many Kidde models do come with an adapter.  

CP wrote at 2012-09-11 14:12:20
We have been having this problem for 7 years on and off.  It was so bad last night I had to look for a solution.  We had been thinking over the years that it was a bad battery, bad unit (we replaced a few last year thinking we fixed the issue.)  Last night at 2, 3 and 4.  Kept going until all units were disconnected and back up batteries taken out.  We will buy different ones today, but we will need an electrician to install because they are all hard wired.

What is worse than no sleep is the fact that my children have learned to sleep through fire alarms!!!!  This product is a danger to families.  BTW our units were installed with new construction 2002/2003 unit is BRK 4120B manufactured May 27, 2002.

Any product that needs a specific battery or it may explode is not worth buying in my mind.  Don't you think they should have a warning on the unit if that is the case??????

BostonDave wrote at 2012-12-06 18:14:27
I am SO GLAD I found this webpage!

My quick point: What about FLASHING LIGHTS at nighttime as a trigger for false alarms in these PHOTOELECTRIC sensors?

[Long Story]

Same problem here, but with wrinkles: First Alert 7010B, which is a newer model (Amazon reviews show that it's usually solid, but four negatives reflect this problem). Also, not coppertop Duracell but ProCell by Duracell. Anyway, I'm out of the house last night and my wife calls me yelling that the alarms triggered around the house 3x between 10:30pm and 12midnight. But the alarm sound was triple-beep/pause/triple-beep/pause/etc. I look it up and it's not the actual alarm, but the test-tone. Regardless, it scared the daylights out of my wife and children. It went on for a minute or two, then stopped itself. This repeated two times more.

So, I read this webpage and my brain starts rolling. Why almost always at night? This morning, I mention my idea to my wife and she blurts out that our 3-year old was playing around with a flashlight last night just before the first alarm sounding. She herself for a moment wondered if it was the trigger, but then she forgot because the boy was so shocked by the alarm that she attended to him.

Anyway, not sure if it's helpful, but an idea...what if a flash of light in a dark room could possibly trigger a DEGENERATING PHOTOELECTRIC SENSOR? I had these for 3 years in a new construction problems until now.

Richard wrote at 2012-12-07 15:35:10
I removed an excessivly hot 9v battery from one of our smoke detctors this morning at about 4am.  The detector was chirping and I thought the battery was just low. To my shock the battery was way too hot to touch.  Not sure of make/model of detector but likely a 2000 - 2002 model.  This was very troubling and I was happy to find this website as I'd never heard of this issue before.

Bob E wrote at 2012-12-22 05:03:11
piece of mess...disconeccted the unit from ceiling and stopped for few nights...started beeping tonight...i cut the wiring still beeping...finally took the battery out of unit i had removed beeping stopped. Now have to redo wiring and replace complete unit.

Tom Eckel wrote at 2013-12-23 22:53:05
I hate to beat a dead horse but we've been having the same problem. I replace all our smoke detector batteries annually now because of this problem. We purchased our house in 2005 new and our BKL 4120B smoke detectors are dated 5/07/2004. We relies the importance of good working smoke detectors because I am a retired New Jersey fireman so BRK wins this one, after reading all the problems with these smoke detectors I'm replacing them.

Juliette wrote at 2014-01-29 02:28:06
I purchased my town home new in 2005 and I also have the problem of the smoke detectors going off in unison for no particular reason and random times.  It is so frustrating and annoying that I have several times wanted to rip them all from the wall.

The original post on this site dates bake to 2006.  Hard to believe that the problem has been so prevalent for so long.  I am going to send this site link to 60 Minutes.

GeorgeB wrote at 2014-10-13 22:40:49
Same problem last night. It did not give the "low Batt" chirp, just went into full alarm, for 2-3 seconds. Then quiet.

Change the battery and all was OK for a few hours then ALL 5 units went into alarm! Put a new battery in and all was quiet again.

Shot some compressed air in the TOP vents (not at the bottom - that's where the sound comes out!), it is quiet for now...but I learned how to unplug the unit from the AC and then take the battery out.

I read that they are good for 10 yrs - mine are 12 yrs old so it might be time to change them all. New model # 9120B.

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Dave Neuweiler


The design and application of burglary and fire systems for homes and businesses. Helping alarm owners understand how their system works. Helping to troubleshoot false alarm problems. Questions about monitoring issues.


Over a quarter century in the industry. Experience in installation, service, and monitoring centers. Training manager for a national protective services company; director of education and training for a national trade organization for for alarm dealers.


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