I have 9120b detectors in my house now. I see these are 9120bff. Do you know what the difference is and will they work?

I don't see a difference that would cause a problem with them communicating with each other. They also look the same. Not sure if this helps, good luck

when is the espiration date?

Thank you for your question. This unit has a 10 yr warranty that starts from the date of purchase.

can you put a ten year battery in this?

I don't see why you couldn't. A 9 volt battery is a 9 volt battery..

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First Alert BRK SMI100-AC Hardwired Smoke Detector with Battery Backup, 6-Pack

Product ID: 72948431

Details

Alarm
Audible
Brand
First Alert
Color
White
Compatible Devices
smoke alarms
Item Weight
9.6 ounces
Operating Humidity
10-95% RH

🔋9V battery backup for power outages

🔗Interconnect up to 18 units for full home coverage

🔧Open mounting design for quick, hassle-free install

€ 280.07

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Sold byAmazon CroatiaDelivered byDesertcartCustomer service byDesertcartReturns14 days · 30 with PRO

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Description

🔥 Stay ahead of danger with the smartest, fastest-install smoke alarms! 🔥

SMART SILENCE TEST - Single button to silence nuisance alarms or test functionality, saving time and stress.
UNINTERRUPTED SAFETY - 120V hardwired power with 9V battery backup keeps you protected even during outages.
BUILT TO LAST A DECADE - 10-year limited warranty ensures long-term peace of mind with trusted First Alert quality.
EFFORTLESS INSTALLATION - Open mounting design and gasket-less base make setup a breeze—perfect for busy pros.
SEAMLESS HOME INTEGRATION - Interconnect up to 18 alarms and devices so your entire home alerts simultaneously.

The First Alert BRK SMI100-AC 6-pack hardwired smoke detectors combine 120V AC power with 9V battery backup to ensure continuous protection. Featuring ionization sensors for rapid fire detection, tamper-resistant locking pins, and interconnectivity of up to 18 units, these alarms deliver reliable, whole-home safety. Designed for quick installation with a gasket-less base and side-load battery compartment, they reduce nuisance alarms and come backed by a 10-year limited warranty—making them the go-to choice for professionals and safety-conscious homeowners alike.

Specifications

ASIN	B07B4CGQLT
Alarm	Audible
Best Sellers Rank	#2,519 in Tools & Home Improvement ( See Top 100 in Tools & Home Improvement ) #15 in Smoke Detectors & Fire Alarms
Brand	First Alert
Built-In Media	9-volt battery (6), First Alert BRK 9120B Hardwired Smoke Alarms with Battery Backup (6), Mounting brackets with hardware (6)
Color	White
Compatible Devices	smoke alarms
Customer Reviews	4.6 4.6 out of 5 stars (1,230)
Item Dimensions D x W x H	2.2"D x 5.6"W x 5.6"H
Item Type Name	Smoke Detectors
Item Weight	9.6 ounces
Manufacturer	First Alert
Mfr Part Number	9120BFF-6
Model Number	9120B
Number of Items	6
Operating Humidity	10-95% RH
Power Source	Battery Powered
Product Style	Hardwired
Sensor Type	Ionization
UPC	029054019387 029054019226
Unit Count	6 Count

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Our prices include the product cost, international shipping, import duties, customs clearance, and local delivery charges. We handle all customs and import procedures, ensuring there are no hidden fees upon delivery. PRO members receive additional benefits including free shipping.

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TrustScore 4.5 | 7,300+ reviews

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Fast shipping and excellent packaging. The Leatherman tool feels very premium and sturdy.

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€ 280.07

Duties & taxes included

In stock

Sold byAmazon CroatiaDelivered byDesertcartCustomer service byDesertcartReturns14 days · 30 with PRO

Buyer Protection · Full refund if your order doesn't arrive as described.

Desertcart purchases this item on your behalf and handles shipping, customs, and support to Croatia.

Secure transaction

Trustpilot

TrustScore 4.5 | 7,300+ reviews

Imran F.

Very reliable shop with genuine products. Will definitely buy again!

2 weeks ago

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Perfect platform for hard-to-find items. Delivery was prompt.

1 month ago

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