First Alert SMI100-AC Hardwired Smoke
A hardwired ionization smoke alarm with a 9V battery backup that interconnects with other First Alert or BRK hardwired alarms. The maker lists it as the replacement for the 9120B.
Alarm spec sheet
| Type | Smoke |
|---|---|
| Sensor | ionization |
| Power | Hardwired with 9V alkaline battery backup (replaceable) |
| Interconnect | Wired |
Listed features
- Hardwired interconnect with up to 12 other First Alert or BRK detectors and 6 other compatible devices
- 9V battery backup
- 10 year limited warranty
Worth checking
- Ionization sensing only
- Voice alerts not offered on this model
Where to buy the SMI100-AC Hardwired Smoke
Prices and availability change. We may earn a commission from some links.
- Check for recalls: Search the agency's recall list with the model number and date code from the label: CPSC recall search.
- Use and supervision: follow the maker's warnings on the product, and see CPSC's Safe Nursery guide. Check the label and the maker's instructions, and ask your pediatrician about your child.
Full specs
| First Alert SMI100-AC Hardwired Smoke | |
|---|---|
| Type | Smoke or CO alarm |
| Alarm | smoke |
| Sensor | ionization |
| Power | Hardwired with 9V alkaline battery backup (replaceable) |
| Interconnect | wired |
Compare the SMI100-AC Hardwired Smoke with
How each closest rival differs from the SMI100-AC Hardwired Smoke, from the makers' specs.
- First AlertSMCO210 / SMCO210V ComboCompare side by side
- First AlertSMCO500V ComboCompare side by side
- First AlertSM210 / SM210V / SM210L 10-Year Smoke10-yearCompare side by side
- First AlertSMCO100 / SMCO200V Combo10-yearCompare side by side
SMI100-AC Hardwired Smoke: questions answered
From First Alert's published specs, last checked 2026-11-11.
Where should the First Alert SMI100-AC Hardwired Smoke go?
Use and supervision: follow the maker's warnings on the product, and see the AAP's safety and prevention pages. Check the label and the maker's instructions, and ask your pediatrician about your child.
Still wondering? Write to us at hello@cribpicks.com and we'll look it up.
More smoke and CO alarms
- First AlertSMICO100-AC Hardwired Combo
- First AlertSC5 Smart Smoke & CO
- First Alert10-Year Battery Photoelectric Smoke Alarm, Slim Profile
- First AlertCO400 Battery Carbon Monoxide Alarm
- First AlertCO605 Plug-in Carbon Monoxide Alarm
- First AlertCO710 Carbon Monoxide Alarm with Digital Temperature Display
Where these specs come from
Last checked 2026-11-11. Spot something wrong? Tell us. Read our editorial and safety policy and corrections.