First Alert SC-9120B Hardwired Smoke and Carbon Monoxide Alarm
with Battery Backup 2 Pack
Price as of 2026-06-02. Check Amazon for the current price.
Quick Decision
Is This Right For You?
- •Buyers who prioritize quality over price in Smoke Detectors
- •Those who want a top-rated option — in the top 3% of Smoke Detectors by rating
- •First Alert loyalists — the brand spans 100 products in our database
- •You're on a tight budget — $31 above the category average of $77
- •Kidde Smoke and Carbon Monoxide Detector — 50% cheaper at $54 (Score B)
📊 Based on data analysis of 37 products in this category.
Mubboo Score: B-
How It Compares
This Product First Alert SC-9120B Hardwired Smoke and Carbon Monoxide Alarm | Most Popular Kidde i4618AC Hardwire Smoke Alarm | Best Rated First Alert BRK Smoke Alarm | Best Value Kidde Smoke and Carbon Monoxide Detector | |
|---|---|---|---|---|
| Price | $107.50 | $178.99 | $98.94 | $54 |
| Rating | 4.8/5 | 4.6/5 | 4.5/5 | 4.1/5 |
| Reviews | 438 | 1,532 | 878 | 1,526 |
| Mubboo Score | B- | B | B- | B |
Quick Specs
- Color
- 2 Units (Sc-9120b)
- Style
- Hardwired Alarm
- Item Weight
- 1.34 Pounds
- Sensor Type
- Electrochemical, Ionization
- Manufacturer
- First Alert
- Model Number
- SC9120B
- Power Source
- Battery Powered, Corded Electric
- Product Style
- Hardwired Alarm
What People Say
Synthesized from 40 reviews · 100% verified purchases.
Test units upon arrival, as included batteries may be dead or drain quickly. Verify activation tab functions and note that sealed-battery models may not interconnect with other alarms.
- Ease of Installation
- Good Value
- Reliable Performance / No False Alarms
- Compatibility with Existing Mounts
- Long Battery Life / No Battery Changes
- Pre-installed Battery Drains Quickly
- Dead on Arrival / Activation Issues
- Flimsy Build Quality
- Confusing Instructions
Expert Picks in Smoke Detectors
- Kidde Smart Smoke Detector — Best smoke detector overall
- First Alert Battery Smart Smoke & Carbon Monoxide Alarm with Nest Protect — Best for Google Nest users
- Kidde Ring-Enabled Smart Smoke and Carbon Monoxide Detector — Best smoke detector for Alexa and Ring users
- First Alert SMI100 Dual Sensor Smoke Detector — Best budget smoke detector
Category recommendations from independent expert publications. Source links in References.
Related Video Reviews
Key Features
- ✦Hardwired CO smoke alarm features battery backup for constant monitoring
- ✦Can connect to other compatible BRK or First Alert CO smoke detectors
- ✦Lights indicate if the alarm is for smoke or for carbon monoxide
- ✦Single test silence button for simple operation
- ✦Side-load battery compartment for convenience
Source: product listing on Amazon.
About First Alert
- 100 products in our database
- Average rating: 4.6/5 across all products
- Price range: $13.98 – $648
- Categories: Carbon Monoxide Detectors, Fire Extinguishers, Smoke Detectors
Other Smoke Detectors
Bottom Line
First Alert SC-9120B Hardwired Smoke and Carbon Monoxide Alarm earns Mubboo Score B-. Priced at $108 — a premium option, above the category average of $77. Rated 4.8/5 from 438+ reviews. Strong buy if: buyers who prioritize quality over price in smoke detectors, those who want a top-rated option. Skip if: you're on a tight budget — Kidde i4618AC Hardwire Smoke Alarm (Score B, $179) may fit better.
Frequently Asked Questions
Is the First Alert SC-9120B Hardwired Smoke and Carbon Monoxide Alarm worth buying in 2026?
It earns a Mubboo Score of B-, with a 4.8/5 rating from 438 reviews — better than 97% of Smoke Detectors we track.
How much does the First Alert SC-9120B Hardwired Smoke and Carbon Monoxide Alarm cost?
It is currently $107.50 — premium-tier pricing for Smoke Detectors.
How does the SC-9120B Hardwired Smoke and Carbon Monoxide Alarm compare to other Smoke Detectors?
The category's most-reviewed alternative is the Kidde i4618AC Hardwire Smoke Alarm (4.6/5, 1,532 reviews, $178.99). The SC-9120B Hardwired Smoke and Carbon Monoxide Alarm carries a Mubboo Score of B- vs B.
Sources & References
Mubboo may earn a commission from purchases made through links on this page. Prices and availability are accurate as of the last sync (2026-06-02) and may change.