First Alert BRK 3120B Hardwire Dual Photoelectric and Ionization Sensor Smoke Alarm with Battery Backup

Reliable Smoke Protection Without the Hassle of Battery Changes I’ve been gradually upgrading the smoke alarms in my home, and this First Alert SM310 has been one of the easiest and most reassuring additions. The 10-year sealed lithium battery is a huge selling point—no more late-night chirping or running out for 9V batteries. Once mounted, it’s basically set-and-forget until replacement time. What I really appreciate is the dual-sensor design. It combines photoelectric and ionization sensors, which means it’s better equipped to detect both fast-flaming and smoldering fires. That gives me more peace of mind, especially with kids in the house and multiple floors to cover. The test/silence button is also handy—easy to reach, and it worked perfectly during my trial run. Installation was quick with the included hardware, and the alarm sits low-profile against the ceiling without looking bulky. The sound output is loud enough to be jarring (as it should be), easily heard through closed doors. If I had to nitpick, I’d say it’s not interconnected, so it won’t set off other alarms in the house if one goes off. For some setups, that’s an important feature to consider. But for standalone coverage—especially in bedrooms, hallways, and smaller homes—it’s an excellent choice. Bottom line: A dependable, no-maintenance smoke alarm with dual sensors and a 10-year battery that delivers both convenience and safety.

As a volunteer firefighter, I look at smoke detectors as an insurance policy. I bought six of these to replace the existing smoke detectors in our eight year old home. The previous detectors started to fail causing random activation at the worst possible times. Think 3 am being fast asleep and the alarms would go off. Batteries changed, old detectors cleaned out with an air duster and still no luck. Since its wise to replace your detectors every ten years or so, I bit the bullet and replaced them all. The wiring in my house allows these to be daisy chained (when one detector is activated a signal is sent to the rest via the house's smoke detection power source) with one another which in my opinion is a good thing. I want to know if a fire has started in another part of the house and the unit closest to me to activate as well. As for this product, it is a little more expensive than other units, but it is well worth it for its dual detection capabilities: photo electric and ionization. They are extremely easy to install and come with all of the necessary hardware. Most houses built in the last 15 years or so have been wired for smoke alarms and these units run off that power source. They come with a low voltage terminal/wire that can be adapted easily to your system if your system has the old contacts. One of the main selling points for me is that the backup power on these units use AA batteries instead of a 9 volt which is the majority of other units. I also purchased two combination smoke alarm/carbon monoxide detectors that are compatible with these units in a systems configuration. All things aside, no more false latch alarms and new units installed that should last me another ten years in the house.

I had an older model BRK 4120B, about 10 years old, which only has one type of sensor. Ionization Smoke Alarms work best at detecting minute particles of fast, flaming fires, but there’s a tradeoff. These typical perform poorly in detecting smoky or smoldering fires. Ionization units have been reported to “false alarm” from charred food, liked an over-nuked pizza, while cooking. Photoelectric Smoke Alarms excel at detecting the bigger particles found in smoldering fires. Photoelectric units generally produce fewer “false alarms” from cooking, but react quickly detecting the smoldering fire types. The First Alert BRK 3120B offers the best of both worlds, using both Ionization and Photoelectric sensors. This way, you’ll get an alarm that detects either type of fire. Some newer Smoke Alarms, except the combo units, also have a built in CO Alarm. At first blush, I thought this might be the way to go, but call me old school, in that I believe it’s better to keep things simple, by having separate Smoke Detector and CO Detectors. Especially, since there are no combo smoke detectors and CO alarms all built in the same unit. My analogy is like when TV’s with integrated VCR’s first came on the scene. (I said I was old school). The TV make work fine, but if the VCR craps out – or vice versa, then you’re faced with a bit of a challenge, an also a higher repair cost, since all the componentry is smaller since it must all fit into the TV “box.” I also checked the rating for the BRK3120B and the Kidde PI2010, also a combo unit. I went with the First Alert because it offered the same reported lab performance at cost savings compared to Kidde. I need 12 alarms, so the cost savings essential got me 12 for the price of 10 from the other guys. Installation was especially easy, since the BRK uses the same size mounting ring (and the quick connect cable) as the ones I am replacing. Not a big deal, but nice nonetheless. Also, maybe a minor point, but the BRK 3120B uses 2 AA Alkaline batteries, compared to the more expensive 9V for the Kidde units. Lastly, be sure to replace any brand of smoke detectors after 10 years from their manufacturing date (usually found on the back of the alarm). Good Luck - I hope this helps.

There's good news and bad news about this product. (Detailed review ahead.) This product is highly rated by the leading consumer testing magazine. And it's priced competitively on Amazon. I ordered 6 of these, and all arrived promptly, packed together, but in individual smaller boxes, all well cushioned. Five of the items arrived perfect, and installed easily (but more info on an important installation detail below). One of these detectors arrived with a significant manufacturer's defect. See the attached photo for a clear illustration of the defect, which made this detector uninstallable. The electrical pins inside the device were improperly positioned. This defect also interfered with the opening/closing of the battery door on the new detector. Amazon handled the exchange promptly and courteously. Now, about the installation of the OK units: There's also good news and bad news. Good news: The connecting pigtails included with the new First Alert smoke detectors are identical to the pigtails in my 10-year-old First Alert same-model detectors, which these are replacing. That means it was not necessary to un-wire and re-wire new pigtails into their wall boxes before replacing each detector. I was able simply to disconnect the old pigtail from the old detector and plug it into the new detectors. Easy! And safe! Bad news: First Alert has very SLIGHTLY modified the round plastic mounting base for the new units, compared to their own 10-year-old design. This means I had to remove the old mounting base and replace it with the new one. It's an easy step, no problem. But because the new mounting base has a smaller diameter (a "trimmer" design), the new bases expose a ring of unpainted/unwalpapered wall/ceiling surface, which requires patching. First Alert has ALSO SLIGHTLY modified the turnscrew plastic locking design of the detector, so it no longer secures completely to the 10-year-old design. This, also, means the old mounting bases cannot simply be left in place, with the new detectors simply attaching to them. In a couple of highly-visible and not-easily-patched wallpaper locations, I decided to leave the old mounting bases in place anyway (preserving the wallcovering's appearance), and discovered that the new detectors ARE able to hang fairly securely (but not perfectly) on the old bases. This is an imperfect workaround, but it DOES work, especially since the detectors are in no danger of falling off the wall (they're hardwired, electrically). Using this method will require a bit of care (a two-handed job) when changing batteries annually, to avoid pulling the detectors off their mounts. But it's not difficult. A final note: Regardless of whether these detectors are attached to their OLD mounts or to the NEW ones, the distinction is invisible from below. In fact, the wallcovering issue with the new, trimmer bases is more noticeable than the new detectors attached to the old mounts.

If you're looking at this alarm, you're shipping for a hardwired, dual photoelectric/ionization alarm and are willing to pay for it - I think that's a smart move and cheap insurance in case of a fire. The main competitor to this model is Kidde's PI2010. Both of these are what I would consider the Cadillacs of smoke detectors. I owned the Kidde model for 8 years in our old house; when we moved, I noticed the detectors were an off-brand company (USI) that were 13 years old. Time to get a replacement. I think this First Alert model is better than the Kidde for a few reasons. First, the battery housing on the First Alert model is accessible without having to remove the detector and the wiring harness, which is required to replace the battery on the Kidde. Not only that, the indicator light on the First Alert model changes to let you know which detector is chirping, something the Kidde model doesn't do. The batteries are also AA batteries, which are cheaper and what we typically have on hand, unlike 9V batteries which usually require a trip to the store once the alarms begin chirping. Second, I think the build quality on the First Alert model is better. The Kidde model was recalled a few years back due to a defect. We didn't really have any issues with false alarms, but the Kidde's reviews seem to indicate that it's more prone to nuisance alarms than the First Alert detector. Installing these was a snap even though we had to remove the old wiring harnesses from the USI detectors and replace them with the First Alert harnesses. No false alarms so far. I'd highly recommend this model.