First Alert SC9120B Hardwire Combination Smoke/Carbon Monoxide Alarm with Battery Backup

by BRK

Product Description

Amazon.com Product Description

The BRK hardwire combination smoke and carbon monoxide alarm detects two hazards with one simple unit. Carbon monoxide (CO) is a colorless, odorless, deadly gas. It can be emitted by sources including gas or oil furnaces, gas clothes dryers, water heaters, fireplaces, wood stoves, charcoal grills, gas ranges, and space heaters. A clogged chimney, improper venting, and attached garages can also cause carbon monoxide accumulation. According to the Consumer Product Safety Commission (CPSC), at least one CO alarm should be installed near a home's sleeping area.

The BRK SC9120 hardwire combination smoke and CO alarm with battery backup includes these features:

• Quick plug-in power connector for easy installation.
• 120-volt AC inter-connectable (with maximum 18 compatible devices). The alarm can be interconnected with up to 12 other compatible smoke alarms and six compatible devices like bells, horns, repeaters and door closers. If one unit triggers an alarm, all smoke alarms in the series will sound. Power indicators show which unit in the series initiated the alarm.
• Ionization sensor which is more effective at detecting flaming fires which consume combustible materials rapidly and spread quickly.
• Microprocessor controlled for fewer nuisance alarms.
• Single test/silence button which both silences a non-threatening alarm or low battery warning and allows you to test the unit's functionality.
• Automatically performs internal test of functionality.
• Latching alarm indicator which automatically identifies which unit initiated the alarm.
• Separate smoke and carbon monoxide visual and audible warnings.
• Battery drawer lock and mounting bracket lock for tamper resistance.
• AC power indicator and alarm indicator light.
• Low battery warning "chirp" and missing battery tab.
• 9-volt battery backup for peace of mind during power outages.

All BRK Electronics carbon monoxide alarms are listed to UL Safety Standard 2034 for residential carbon monoxide alarms. Includes 9-volt backup battery. 5-year limited warranty.--Bree Norlander

What's in the Box
One combination smoke and CO alarm, one 9-volt battery, and user's manual

Product Details

Smoke Sensing Technologies Information [46kb PDF]

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Carbon Monoxide Information [39kb PDF]

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Fire Detection and Protection Fact Sheet [27kb PDF]

• Product Dimensions: 5.6 x 2.2 x 5.7 inches ; 10.4 ounces
• Shipping Weight: 1 pounds (View shipping rates and policies)
• Shipping: Currently, item can be shipped only within the U.S. and to APO/FPO addresses. For APO/FPO shipments, please check with the manufacturer regarding warranty and support issues.
• ASIN: B000HEC4EO
• Item model number: SC9120B
• Average Customer Review: 3.9 out of 5 stars  See all reviews (78 customer reviews)
• Amazon Best Sellers Rank: #149 in Home Improvement (See Top 100 in Home Improvement)
  • #4 in Home Improvement > Safety & Security > Fire Safety > Combination Smoke & Carbon Monoxide Detectors
  • #7 in Home Improvement > Safety & Security > Fire Safety > Carbon Monoxide Detectors
  • #16 in Home Improvement > Safety & Security > Household Sensors & Alarms

Customer Reviews

Most Helpful Customer Reviews

50 of 53 people found the following review helpful:

4.0 out of 5 stars Definitely an upgrade -- and a simple swap, too!, July 16, 2008

By 

ck "moonshadow" (Hawaii nei) - See all my reviews

Amazon Verified Purchase

This review is from: First Alert SC9120B Hardwire Combination Smoke/Carbon Monoxide Alarm with Battery Backup (Tools & Home Improvement)

Our house was wired for smoke detectors -- specifically the rather cheesy BRK 4120SB, which delights in false "low power" chirping. My goal was to replace the ones in the bedrooms with combination alarms that would alert us not only to smoke but to the presence of carbon monoxide. (Not to scare you but harm and even death from carbon monoxide poisoning are definite risks, especially in a home with deep-sleeping teenagers.)

I needed units that would be compatible with the wiring of our current system, and ideally ones that would accept the power leads, as wired. After some research here and elsewhere, I called the BRK help line and got definite information about the unit that would be compatible, as well as locations within the home where I both should and should not install units.

I ordered two units to start with, still being a bit leery of my previous experience, and can say that installation took less than 5 minutes per device.

1. Follow the instructions for removing the plastic tab in the battery door of your new unit and pushing the button to test your new unit. If all's well, proceed. Disregard the "locking pin" stuff unless you are in a shared dwelling and are concerned with someone walking off with your 9-volt battery. (This was the weirdest part of the instructions, frankly, and this is my guess on why it's there.) **Important: you are listening for 3 tones, pause, 3 tones, pause, 4 tones, pause, 4 tones. There is a typo at the bottom of page 3 of the instructions, so I've just verified with BRK that the tone pattern I'm mentioning is the correct one.

2. Twist off and unplug your current unit.

3. Back the two screws holding your collar to the ceiling so you have enough clearance to remove the collar.

4. Install the new collar.

5. Install your new unit. (A wired plug is included in case you need to swap your existing plug for the new plug.)

Fellow owners of the 4120SB will find that the upgraded unit sets and locks into place in the ceiling *much* easier and more reliably. Ditto with the battery door. Note that on the SC9120B, if you're having problems with the battery door not shutting (a) there is a little trigger tab that you should be able to push down with a fingernail and/or (b) hold the unit upside-down.

***A word, please, about longevity, since the primary purpose of an alarm is your safety.

1. Replace your batteries at least once a year.

2. Combo smoke/carbon monoxide units have a 5-year life span, per BRK staff. Regular smoke alarms have a 10-year lifespan. Not replacing them within these timespans is, in my opinion, the most dangerous kind of false economizing. (Note also that if you need help, the BRK customer service apparently has improved greatly since the experience of earlier reviewers of the product line. The call I made in June could not have been more thorough and professional, even to dealing with the phantom beeps of my 5-year-old alarms.)

3. Whether or not you buy this or any smoke alarm product, please do yourself and your family two favors. First, label the plug (hidden) side of your units with the install and replace dates. Second, change your batteries at least once a year.


BTW, I gave the unit a 4 rather than a 5 because while the battery door and twist-on/twist-off issues are less irritating than on the earlier generation, they still do exist.

33 of 39 people found the following review helpful:

1.0 out of 5 stars No Zero Stars Option - Alarm Resulted in Massive Property Damage, December 21, 2010

By 

Juana "Juanita Beasley" (Baltimore, MD United States) - See all my reviews

This review is from: First Alert SC9120B Hardwire Combination Smoke/Carbon Monoxide Alarm with Battery Backup (Tools & Home Improvement)

I have a rental property and this year, the city's new regulation required installation of these detectors. One of the detectors malfunctioned and the terrified tenant called 911, who proceeded to do over 1000 dollars in property damage.

I subsequently found out that even the EPA has admitted that many of the CO detectors they tested were unreliable, and either went off at too low of a level or did not sound at dangerously high levels.

According to their website, the best way to keep the building's inhabitants safe is to have fuel-burning appliances properly installed and maintained by licensed professionals to make sure that the gases (including CO) are vented properly.



I ended up doing a lot of research related to CO as a result. I have the documentation from the Fire Department indicating the levels that they measured (WAY BELOW the low threshold on the detector) even near the detector.

I knew that a problem was unlikely since the heat wasn't even ON at the time.

Nevertheless, they broke into two apartments, destroying irreplaceable historic doors and frames. Even the fire chief told me that if I have a hard-wired smoke detector/CO detector combo, I should get it replaced as they have had false alarms with that type of detector. But as mentioned on the EPA website, and evidenced by many other reviews on Amazon etc, CO detection is apparently in it's infancy and I'm surprised that these detectors are even being sold, much less required by law.

Unfortunately, according to my lawyer, it's more trouble than it's worth to sue the city, so I had to suck up the CONSIDERABLE expenses myself. Not to mention my poor tenant, who was (unharmed of course) but anxious.

I am so ANGRY, but the only thing I can do apparently is to WARN other people about these alarms. If you have one in your house and there's a false alarm, that's one thing. But if a tenant has a false alarm, you are vulnerable in many different ways.

The WORST thing about this type of alarm is that if the CO part malfunctions, you've lost your smoke alarm as well. In addition, since it's installed high on the ceiling, if it false alarms, you have to get on a ladder to turn the thing off.


I would not recommend the first alert smoke/CO alarm to ANYONE.

22 of 25 people found the following review helpful:

1.0 out of 5 stars Stay clear of this headache, February 7, 2009

By 

James L. Dunn - See all my reviews
(REAL NAME)   

This review is from: First Alert SC9120B Hardwire Combination Smoke/Carbon Monoxide Alarm with Battery Backup (Tools & Home Improvement)

Received three BRK SC9120B replacements after original units (4 years old) started a low battery chirp with new Duracell batteries. Spoke with BRK rep. about problem and they sent three new units with Duracell batteries. The units worked fine for about two weeks before all three started to chirp a low battery signal. In that time our other three BRK smoke only detectors that were installed 4 years ago started the same chirping sound. Again called BRK and they were going to send us three replacements for them. After the nightmare of having six four year old BRK products fail in a matter of three weeks and three brand new replacement units fail in two weeks. I would stay away from BRK! I have read elsewhere about an issue with BRK and Duracell so I was a bit surprised when the new units arrived with Duracell batteries in them.