Customer Reviews For The First Alert Hardwired Smoke Alarm with Battery Backup

Overall Rating

802 Reviews
798 customers recommend this product
Hiram H
May 1, 2024
Verified Purchase
Excellent Price and Easy to install

All you need in the box. Is wired and interconnected with an easy to access 9v battery for easy battery change. Install 4 of them in my apartment and they are working really well. Will buy again for sure.

James R
April 13, 2024
Verified Purchase
Proven Product

It just works! This is the only brand I trust with my life.

John W
April 11, 2024
Verified Purchase
first alert smoke alarm

very good product that last s up to 10 years

Siavash M
April 5, 2024
Verified Purchase
Exactly what they said it would be . I'm very happy

The product was exactly as it said it would be , fast shipping! I am totally happy and I’m planning on ordering more! Thank you First Alert!

cheryl c
February 27, 2024
Verified Purchase
Excellent products

I ordered four to replace my old ones. Super easy to install. As always, make sure you have turned the breaker off prior to replacing/installing.

Mike A
February 5, 2024
Verified Purchase
The best choice

I have ordered this product in the past very pleased. Just moved to New home and had to replace some of the smoke detectors. I got 5 of this product and quality and ease of installation is amazing. Highly recommended. Ordering and service was excellent.

Adrien B
January 15, 2024
Verified Purchase
Fire alarm

Great fire alarms. Just needed to replace 10+ year old ones in my apartment.

Jackie S
December 31, 2023
Verified Purchase

Easy to install. Fast shipping.

Linda Y
December 11, 2023
Verified Purchase
Smoke alarms

These are the best and easiest to install. Great product and great service. Thank you

Mike A
December 11, 2023
Verified Purchase
Best choice

The best quality, reasonable price fast service.

Doug S
December 4, 2023
Verified Purchase
Easy Installation

Easy to install if you have minimal electrical knowledge. Just be sure your power is turned off to avoid electrical shock. If you are not comfortable around electricity hire someone who is qualified. A+++

Suzanne L
November 6, 2023
Verified Purchase
Excellent service

I was very pleased start to finish with my order. These are very easy to install. Excellent customer service

Pamela H
October 30, 2023
Verified Purchase
First Alert Hardwired Smoke Alarm

I purchased this product from First Alert Store to replace an alarm that had aged out. The price was very reasonable, it shipped and arrived very quickly and it was easy to install. What more could you ask for!? I will be buying all of my smoke alarms from them.

May 19, 2023
Verified Purchase

The 9120B smoke alarm arrived promptly and was very easy to install. I am very satisfied with the purchase.

John W
May 2, 2023
Verified Purchase

Easy product to install and was shipped right away!

Elizabeth M
April 21, 2023
Verified Purchase
Perfect fit and received quickly

Alsome fast and reliable products

Elizabeth M
April 10, 2023
Verified Purchase
Perfect fit and received quickly

Alsome fast and reliable products

Sandy P
March 23, 2023
Verified Purchase
Smoke detector

I love my First alert smoke detector. I love the fact that I can order directly from the company and not have a middle middleman.

Kenneth C
March 15, 2023
Verified Purchase Helpful
Easy to Install

Just installed the 9120B Smoke Alarm after painting the hallway celling. This model was the replacement for the smoke alarm that was installed in the celling since 1992, it was really time to update it and it was very easy to do. The alarm looks great and it appears to be doing what it suppose to do, monitoring for a fire. I like it, no false alarms and I think it will last 10 years with no problem.

Laurna C
March 14, 2023
Verified Purchase
Great product

Great product, easy to install and price is great when comparing to others.

What is the proper placement of smoke alarms?
It is important that you have the proper placement for your smoke alarms. Install your alarms at least 20 feet from appliances like furnaces and ovens, which produce combustion particles. Alarms should be at least 10 feet from high humidity areas like showers and laundry rooms, and at least 3 feet from heat/AC vents. Be sure to install a smoke alarm in each bedroom, one at the top of each stairwell, and one on every level.
Why doesn't my smoke alarm sound when I push the test button?
It is important that you frequently test your smoke alarms. When you are testing your smoke alarm, there are a number of reasons why the alarm might not sound:
  • You may not be holding the test button down long enough. Try holding it down for up to 10 seconds (20 seconds on photoelectric models) .
  • Your battery may not be installed properly or snapped all the way in place. Even if the alarm sounded briefly when the battery touched the terminals, you still need to make sure it is snapped securely in place. If the battery is loose, in cannot power the smoke alarm properly. After installing new batteries, be sure to test your smoke detector.
  • Your AC power may not be on. AC and AC/DC units will have a power indicator light (red or green) that shines continuously when they are receiving electrical power.
  • If you have a 10-Year model, the smoke alarm may not have been properly activated. If the tab broke away before the alarm was activated, you can use a toothpick to move the switch over to test the alarm.
Why does my smoke alarm go off when I install a battery or turn on the AC power?
It is normal for smoke alarms to go off and sound briefly (up to 5-10 seconds) when you install a new battery or when they are powered up. If the alarm continues to go off and no smoke is present, the cause may be one of the following:
  • There may be insufficient battery power, try new batteries.
  • Problems with voltage or insufficient electrical power (brown out) may cause a continuous weak sounding alarm. For AC or AC/DC models, temporarily disconnect power at the service panel until the brown out is over. If you do not restore the AC power, your smoke alarms cannot warn you of a fire.
  • Incompatible warning device. If an incompatible alarm or auxiliary device is linked into a series of AC or AC/DC smoke alarms it may cause the system inadvertently go off.
I lost my First Alert smoke alarm owner's manual. How can I get a new one?
First Alert smoke alarm owner's manuals are available online for download at no cost. Find your alarm in our Smoke Alarms section.
Why does the National Fire Protection Association (NFPA) recommend that home smoke alarms be replaced after 10 years?
Smoke alarms have a limited life. Although each smoke alarm and all of its parts have passed many stringent tests and are designed to be as reliable as possible, any of these parts could fail over time. Therefore, you must test the devices weekly. The unit should be replaced immediately if it is not operating properly. The performance of smoke alarms older than 10 years is simply not reliable. To ensure your family's safety, all carbon monoxide and smoke/CO combination alarms need to be replaced every 5-7 years. All smoke alarms need to be replaced every 10 years.

Hardwired Smoke Alarm with Battery Backup:

Designed to help promote household safety, the First Alert 9120B Hardwired Smoke Alarm with Battery Backup can provide a vital early warning of fire. This hardwired smoke detector uses an ionization smoke sensor to reliably detect smoke from hot, fast-flaming fires.

Ionization Sensor Reliably Detects Flaming Fires

The First Alert 9120B Hardwired Smoke Alarm with Battery Backup comes equipped with an ultra-reliable ionization sensor to provide the earliest possible warning of a fast-flaming fire. The sensor is optimized to detect flaming fires, such as those caused by paper, kitchen grease, and other fast-combusting materials.

Gasket-less for Easy Installation

To facilitate hassle-free installation, this smoke alarm features a streamlined mounting system with a gasket-less base. The mounting bracket keeps the alarm secure over a wide rotation range while maintaining perfect alignment. The alarm also comes with a dust cover to keep the unit clean during construction. AC-powered smoke alarms must be installed in accordance with all local electrical codes.

Battery Backup for Detection During a Power Outage

This smoke alarm is designed for hardwired installation, but it also features a battery backup that helps ensure continued functionality in the event of a power outage. The unit comes with a 9-volt battery and features a pivoting, easy-to-access battery drawer that allows you to replace the battery without dismounting the alarm.

Works in Tandem with Other First Alert Alarms

In addition to functioning independently, this smoke alarm can also integrate with up to 12 other First Alert or BRK hardwired alarms for coverage of larger spaces. It also integrates with up to six other compatible devices, such as bells, horns, and repeaters. If one alarm in the series is triggered, they will all sound. The alarm features a latching indicator to identify which unit triggered the alarm, alerting you to the area of danger.

First Alert Smoke Alarm 9120B

Recommended replacement for the following obsolete models:

BRK 4120B
BRK 4120SB
First Alert SA4120B
First Alert SA4121B
First Alert SA4919B

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