First Alert Hardwire Smoke Alarm
- Smoke Detectors & Fire Alarm
- More reviewed than 70%
A practical hardwired replacement alarm for interconnected home systems, with battery backup for power outages.
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How it ranks among the 10 smoke detectors & fire alarms we track
4.5★ across 2,600 Amazon ratings, Bayesian-smoothed toward the category average.
2,600 Amazon ratings, weighted on a log scale so huge counts don't drown everything.
7,000+ bought on Amazon last month.
Brand identity, imagery, description and spec coverage.
The ProductDome score is separate from the Amazon rating shown above: it combines the Bayesian-smoothed Amazon rating with evidence volume, tracked demand, and data quality across the 10 smoke detectors & fire alarms we track - how the scorecard works · full smoke detectors & fire alarms data report. Confidence: limited - incomplete product information.Updated 7 days ago. Data-computed, not a hands-on test. Compiled by the ProductDome Research Team.
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.
Strengths and trade-offs
Drawn from this product's published specifications.
- 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 |
Other First Alert smoke detectors & fire alarms
How it compares
This product against the closest alternatives we track in smoke detectors & fire alarms.
| Product | Amazon rating | Ratings | ProductDome score |
|---|---|---|---|
| First Alert Hardwire Smoke AlarmThis product | 4.5 / 5 | 2,600 | 2.7 / 5 |
| X-Sense Smoke Detector Carbon Monoxide Detector ComboX-Sense | 4.5 / 5 | 4,200 | 4.5 / 5 |
| Kidde Compact Smoke DetectorKidde | 4.5 / 5 | 940 | 4.3 / 5 |
| Kidde 21007584 I4618 Firex Hardwire Ionization Smoke Detector with Battery BackupwhiteKidde | 4.3 / 5 | 398 | 4.2 / 5 |
| Kidde Smoke DetectorKidde | 4.0 / 5 | 1,400 | 4.2 / 5 |
Similar smoke detectors & fire alarms from other brands
Questions about the First Alert SMI100-AC
Common buyer questions answered straight from the product spec data - no fluff, no "it depends".
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.