Smoke/Carbon Monoxide Detector Recommendations?


Corporate Member
A Duke Energy transformer up the road went south last week. When power was restored an hour later, the Firex smoke detector in the basement went bonkers, continuously sounding the alarm. This alarm is interconnected with a second alarm upstairs, which was going off also. The upstairs detector works as it should, with the basement unit unplugged.

I want to replace both units with a combo photo/ionization/carbon dioxide fire detectors. Consumer Reports lists 4 recommended models, but each has multiple reviews complaining of false alarms though some are because of the detectors being mounted near bathrooms, etc).

What are ye NCWW'ers using in your humble abodes?


Senior User

I cannot wholeheartedly recommend my approach since it doesn't meet code. My house is over 50 years old so it didn't come with detectors. I added a combination unit for my bedroom, the only one on the first floor, and for the older upstairs bedroom. They are not interconnected and are battery operated.

My other two bedrooms upstairs and the smoke detectors were wired in by the contractor who did the rough work. I put in 110V detectors without battery backup. But I recently partitioned off part of one big room up there into the 4th bedroom and put in a battery unit with a 10 year battery. When the battery goes bad it will be time to replace the unit.

I thus have detectors that will work without power but it isn't all my detectors. I HATE the fact that the battery always goes bad at night, when it is cooler, and if the detectors are interconnected all them go off until you find and replace the battery. I wanted to avoid as much of this nonsense as I can. I think all houses should have smoke detectors but I don't agree that 110V units with battery backup and all interconnected are really necessary. Just my opinion (which only counts for my house).



Senior User
After thirty years with my basement shop I decided a fire detector would be a good idea. Like all of you I have seen more than one shop go up in smoke. My plan (still unfolding ) was to install hardwired detectors which I did in three places on the ceiling. I was then going to turn on an intercom monitor so I could hear the alarm if it went off. That idea so far is a bust. Intercoms buzz and pop and create marital tension. I am stuck trying to find a way to get the sound upstairs. Most baby monitors say they won't work in a basement. I wired the detectors through a switch so they are off when I'm working.
I have had the hardwired detectors upstairs all along with no false alarms except opening the oven door when the pizza is done.


Corporate Member
According to the NFPA, smoke detectors are good for about 10 years before needing replaced.

Ionization detectors are the least expensive, and are designed to alarm for fast burning fires (ex: Kitchen stove fire, burning waste basket, etc). Because of their technology, these are the most prone to false alarms from dust, steam, smoking pizza, etc. In tests. they were up to 30 minutes slower on detecting smoldering fires (ex, short circuit in a wall socket, cigarette in a couch cushion). They contain a radioactive element, so are not to be disposed of in the trash.

Photo -electric are designed to detect smoldering fires. In tests, they were up to 30 seconds slower in detecting a fast burning fire. They are less prone to false alarms. Can be thrown in the trash after removing any batteries.

As single use, the above are required to be certified by an outside lab. Multi-use units are only required to have the manufacturer have a testing/certification program.

CO (Carbon monoxide) detectors are good for about 7 years before replacement. If you have a combo unit, it needs replacement at the 7 year mark.

The units with the sealed 10 year batteries (most expensive) do not always make it to the ten year mark. Numerous people have had them go dead in 6-8 years and combo CO units as short as 5 (they are only rated for 7 years).

The theory around the inter-linked alarms is that, with one required in every bedroom, they will alert anyone sleeping or behind closed doors to a situation anywhere in the house. If an inter-linked system goes off, the alarm initiating it is the only one that hitting the reset, (opening the battery compartment if that is the fault) will silence them, so if that is a problem, that should key you in on the alarm/location you need to check. If in doubt as to the cause, call 911 and get everyone out of the house.

Our volunteer fire dept gets several calls a month on average for alarms. Most are "false" alarms, however some of those are in fact accurate alarms caused by someone burning food on the stove. Of the truly false alarms, many are solved by replacing the batteries. One of these was an interlinked system, and the alarm at fault was on a cathedral ceiling, thus hard for the home-owner to access for routine battery replacement. If you have an alarm that you can't get to (a stairwell ceiling is another problem location), I recommend you re-locate it. A few were because the alarm was "chirping" for low battery, and the occupant didn't know what that signified. In one case, we discovered that the hardwired, interlinked alarms were a few years past the 10 year mark. The owner was new, having just moved in a week before, and so didn't have any idea how old the alarms were. Although we only found one bad detector, we recommended she replace all of them.

If your alarm has AA or AAA batteries, I recommend you replace them every 6 months. If nine-volt back-up, once a year.

As for my choice when I replaced mine last year (yeah, I was overdue a few years), I put photo-electric in the bedrooms, and a combo ionization/CO alarm in the hallway outside the bedrooms. Mine are interlinked hardwired with battery back-up. In newer homes like mine, the bedrooms should be protected from an electrical short with arc-fault circuit breakers, but I will leave it to the electricians to discuss the reliability of arc-fault breakers.

Hope this helps, from just another anonymous guy on the internet.
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Senior User
I don't worry about my shop starting a fire. The gas and the other petroleum products in the car in my car garage is a lot more dangerous than the wood in my shop. Neither garage has a smoke detector. I don't remember ever seeing one in a garage.


I use the Kidde combo AC/battery alarms. No problems with the baths as when showering, you should turn on the fan. The one right outside our master bedroom is also just off the kitchen. Drives me crazy as even with the hood going, it trips sometimes. This is not a false trip, just that sensitive. I keep a broom handle handy to reset it.

They should last 10 years, but I put in new ones 3 years ago when I moved in and had to replace one for intermittent chirps even after a new battery.

Any of them can load up with dust. Fumes from painting can damage the sensors.

I believe here in OC, an enclosed garage needs a smoke and CO by code if it is attached. Not sure if free-standing.

I have a CO alarm in my shop as half of it is where I do my other hobby, British sports cars. It reminds me I can only run a car seconds before I need to open up. Don't have a smoke in there as if I was in it, I woudl know it and if I was asleep in the house, I would not hear it. ( disconnected buildings)

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