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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:
First Alert SA4120B
First Alert SA4121B
First Alert SA4919B
Average Customer Rating Based on 127 reviews:
Reviewer: Diane Lyle
Great Job. Order was easy and received right on time. Thank you very much
fast service - 11/06/2018
Reviewer: Dawn Cinker
love the ease of ordering and the fast shipping.
My Saturday Afternoon - 11/06/2018
Reviewer: Anthony DiSanto
Changed out 10 year old detectors with these units, simple. All 10. They look nice, cause my wife said they had to be nice looking, really! ok fine. It's Saturday and it might be date night so... Actually I had her replace one or two. Easy battery replacement access, interconnected testing modes, cute lights and not expensive. One note, this model use ionization so you might want to use a photodect model in your kitchen like I did since even turning the oven on made it go off. Maybe I should get her to clean oven, no! Different model, same brand and of course it look the same. Enjoy you Saturday!
Exact replacement - 11/03/2018
Reviewer: Bruce Hettleman
This unit was purchased to replace an aging but identical unit that continued to beep after battery replacement. The old unit was dated 2011. Must have timed out. New unit stopped the problem. It was very reasonably priced and fits the old wiring exactly. Quick fix. I bought an extra one.
Good product - 11/02/2018
Reviewer: DOUGLAS LADD
Good product. Have had 10 running well for 20 years. Had to replace 2 and they are working just fine. Fast delivery Thanks.
Reviewer: Dawn Cinker
Quick service, perfect replacement for our old alarm
Very Good - 10/22/2018
Reviewer: Judith Golab
I was surprised with quick phone support validating the model I need to replace I was correctly ordering. All items arrived quickly - easy install and came with batteries- surprised. Recommending to all friends replace units - you will feel safer - mine were 14 years and over due
Great Product - 10/18/2018
Reviewer: Richard Dimmick
USPS managed to smash padded envelope smoke detector was packed in but detector OK.
Good - 10/18/2018
Reviewer: Jie Zhang
I bought it to replace a malfunction one which was 6 year old.
Alarm meets needs - 10/03/2018
Product was a replacement for an older version. Installation was easy. Will know if very good is warranted when and if situation occurs.
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