First Alert SC9120B Hardwired Smoke and CO Alarm 2 Pack
- Pack of 2 alarms
- Smoke and carbon monoxide in one unit
- Hardwired, with battery backup
- Photoelectric smoke sensor
Updated 15 days ago · Based on the Amazon listing and published specifications, not hands-on testing.
A straightforward replacement pair for homes already wired for hardwired alarms; the listing is thin, so check connectors and battery type against your current units before ordering.
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ASIN: B01K0IVVW2Model: SC9120BCategory: Combination Smoke & Carbon Monoxide Detectors
Overview
A photoelectric smoke sensor and carbon monoxide detection share one housing in each First Alert SC9120B alarm. The unit wires into household power and falls back on a battery when the power drops.
Two detectors in one housing means fewer devices on the ceiling, and two units arrive per pack. House power with a battery fallback stays on during outages. The listing leaves out battery type, dimensions and interconnect details, so expect to confirm those with First Alert.
Who it's for
Replacing aging wired smoke alarms with combination units, two at a time, is the job here. Rooms with no wiring to the ceiling need a battery-only model instead.
Pros and cons
- Smoke and CO detection in one unit
- Two alarms per pack
- Battery backup during power loss
- Photoelectric smoke sensing
- Battery type not listed
- Requires a hardwired circuit at each location
- Sparse product details in the listing
Performance notes
Each alarm draws house power and switches to its backup battery when power fails, so detection continues through an outage. The photoelectric sensor responds to smoke that scatters light inside its chamber, while the carbon monoxide side senses a gas that smoke sensors cannot.
Specifications
| Brand | First Alert |
|---|---|
| Model | SC9120B |
| Power Source | Battery |
| Sensor Type | Photoelectric |
| Unit Count | 2 |
| Product Style | Hardwired Alarm |
| Mfr Part Number | SC9120B |
Frequently asked questions
How large is the First Alert SC9120B alarm?
The listing does not give dimensions. Compare the mounting plate on your current alarm with First Alert documentation before swapping.
Does the First Alert SC9120B work during a power outage?
Yes. It is hardwired with a battery backup, though the listing does not name the battery type.