First Alert 9120B / SMI100-AC Smoke Detector — 3-Pack, Hardwired Alarm with Battery Backup

Smart, reliable protection for every level

The First Alert 9120B 3-pack blends hardwired operation with a dependable battery backup, giving you coverage across multiple rooms and levels. Designed for straightforward installation and low maintenance, these alarms aim to reduce nuisance alerts while keeping warning times clear and consistent.

With an ionization sensor tuned for fast flaming fires, these alarms respond quickly to evolving conditions. The 120-volt interconnectable design supports up to 18 compatible devices, so one triggered unit can alert all connected units in the series, creating a unified warning network for the home.

Core benefits and practical use

• Hardwired with a 9-volt battery backup ensures ongoing monitoring during power outages
• Ionization sensing helps detect fast flaming fires and alerts you with a clear alarm
• Interconnection supports up to 12 alarms and six accessory devices like bells and horns
• Single test and silence button with a side-load battery compartment simplifies routine checks
• Tamper-resistant mounting bracket and gasketless base enable secure installation and precise alignment
• Dust cover protects the unit during construction and keeps the sensor unobstructed

In real-life scenarios, place a unit on each level and in bedrooms to create a consistent alert network. The design supports quick mounting and straightforward maintenance, which can be helpful for busy households and rental properties with multiple living areas.

Durability, standards, and ongoing value

• UL tested with a 10-year limited warranty for long-term reliability
• Easy installation with universal mounting brackets and a secure mounting system
• Maintenance-friendly features may help minimize nuisance alarms and keep alerts ready

While no alarm guarantees protection, this BRK First Alert configuration offers practical, scalable coverage that can help you respond promptly to potential fires and maintain a safer living environment without overreacting to every alert.

For best results, install one on every level, in key living areas, and in bedrooms, following local building codes and the included mounting guidance.