First Alert SMI100-AC Hardwire Smoke Alarm
- Power Source: Corded Electric
- Sensor Type: Ionization
- Alarm: Smoke Alarm
- Product Style: Precision Detection
Last refreshed Sep 8, 2026 · Based on the Amazon listing and published specifications, not hands-on testing.
A practical hardwired replacement alarm for interconnected home systems, with battery backup for power outages.
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ASIN: B0CJMN3443Model: SMI100-ACCategory: Smoke Detectors & Fire Alarms
Overview
The First Alert SMI100-AC is a hardwired smoke alarm with a 9V battery backup, designed to interconnect with other compatible hardwired alarms so that one triggering sounds them all through the house.
A Quick Connect Plug is included specifically to avoid rewiring during installation, which matters when swapping an old hardwired alarm for this one on an existing interconnect circuit. An indicator light also identifies which specific unit in the chain triggered the alarm, useful once several are wired together.
- Hardwired with 9V battery backup
- Early warning interconnect
- Alarm indicator light
- Quick Connect Plug included
Who it's for
Suited to someone replacing an existing hardwired, interconnected smoke alarm or wiring a new interconnected system across multiple rooms. Not the right fit for a simple stick-anywhere battery alarm.
Pros and cons
- Hardwired with 9V battery backup for outages
- Interconnects with compatible alarms, all sound together
- Indicator light shows which unit triggered
- Quick Connect Plug included, no rewiring needed
- Smoke detection only, no carbon monoxide sensing
- Requires existing or new household wiring
Performance notes
Precision Detection sensing aims to cut cooking-related nuisance alarms while catching real fire conditions early. Through the early warning interconnect, any alarm on the circuit sounding will trigger every compatible connected alarm, and an indicator light identifies which unit started the alarm, which helps pinpoint the hazard's location in a multi-alarm home.
Specifications
| Brand | First Alert |
|---|---|
| Model | SMI100-AC |
| Dimensions & fit | |
| Item Weight | 0.6 pounds |
| Item Dimensions D X W X H | 5.6 × 5.6 × 1 inches |
| 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 |
| Number Of Items | 1 |
| Mfr Part Number | SMI100-AC |
| Builtin Media | Easy Adapter Plug, 9V Alkaline Battery |
| Item Type Name | Smoke Alarm |
| Item Highlight | SMI100-AC, 9V Battery Backup |
Closest rivals on specs
Universal Security Instruments MI106S Hardwired Smoke Alarm- Item Weight 0.6 vs 0.49 pounds (+22%)
Frequently asked questions
Does the First Alert SMI100-AC need rewiring to install?
No, it includes a Quick Connect Plug so it can be installed on an existing hardwired circuit without rewiring.
What happens if one SMI100-AC alarm goes off in a connected system?
Through the early warning interconnect, every compatible connected alarm will sound, not just the one that detected smoke.
What is the battery backup for on the SMI100-AC?
It uses a 9V battery to keep the alarm working during a power outage, since the primary power source is hardwired.