First Alert SMI100-AC Hardwire Smoke Alarm
- Hardwired, corded electric power
- 9V battery backup included
- Easy adapter plug included
- Ionization sensor, smoke alarm
- 5.6 by 5.6 by 1 inches
- 9.6 ounces, white
Last refreshed Sep 8, 2026 · Based on the Amazon listing and published specifications, not hands-on testing.
A hardwired ionization smoke alarm with a battery backup and an adapter plug in the box. It senses smoke only, and the listing gives no interconnect detail.
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ASIN: B0CJMN3443Model: SMI100-ACCategory: Smoke Detectors & Fire Alarms
Overview
A homeowner with a wired smoke alarm circuit gets a First Alert ionization alarm that runs on house power and carries a nine volt alkaline battery as backup. An easy adapter plug is listed with it.
Its strength is mains power with a battery to cover outages, so the alarm stays live when the circuit does not. The limitation is thin detail: no interconnect count, no carbon monoxide sensing and no wiring instructions are listed.
Who it's for
Houses with existing smoke alarm wiring and owners replacing or adding a wired alarm are the audience. Anyone without a wired location, and anyone who needs gas or carbon monoxide detection, should look at a different type.
Pros and cons
- Hardwired mains power
- Battery backup included
- Easy adapter plug listed
- Ionization smoke sensing
- Smoke only, no carbon monoxide
- Wiring instructions not listed
Performance notes
House power runs the sensor day to day, and the battery takes over only when the circuit drops, so the backup battery needs periodic checking. An ionization sensor reacts fastest to quick flaming fires.
Specifications
| Brand | First Alert |
|---|---|
| Model | SMI100-AC |
| Dimensions & fit | |
| Item Dimensions D X W X H | 5.6 x 5.6 x 1 inches |
| Item weight | 9.6 ounces |
| Power & efficiency | |
| Power Source | Corded electric |
| Construction & materials | |
| Color | White |
| Included components | |
| Unit Count | 1 |
| Other details | |
| Sensor Type | Ionization |
| Alarm | Smoke alarm |
| Product Style | Precision Detection |
| Builtin Media | Easy adapter plug, 9V alkaline battery |
Closest rivals on specs
Kidde 10SDR Compact Smoke Detector- Item Weight 0.6 vs 0.39 pounds (+54%)
Frequently asked questions
Does the First Alert SMI100-AC need an electrician to install?
The listing says hardwire with an easy adapter plug but gives no wiring steps or licensing note. Check local rules and the printed instructions before connecting it to house power.
What happens to the SMI100-AC in a power cut?
The listing includes a 9V alkaline battery as backup, so the alarm can keep sensing when mains power drops.
Does the SMI100-AC sense carbon monoxide?
No. The alarm type is smoke with an ionization sensor.