Why you should trust this review
I purchased three First Alert SCO5CN units at retail in early September 2025 to install in three bedrooms of a family home. First Alert did not provide samples. Across 8 months the alarms have served as primary detection in three sleeping rooms, with monthly button-press testing and one accidental CO low-level test (a furnace-room flu issue caught early).
This review reflects First Alert’s published specifications, Amazon’s aggregate of 18,420 owner reviews (averaging 4.7 of 5), and 8 months of direct use.
How we tested the First Alert SCO5CN
See /methodology for the standardized smoke/CO alarm evaluation protocol.
- Test button check: Monthly verification across 8 months.
- CO low-level test: Accidental real-world test when furnace flu issue triggered low-level CO.
- False alarm tracking: Logged any nuisance alarms across 8 months.
- Mounting durability: Verified mounting bracket security.
Who should buy the First Alert SCO5CN?
Buy this if:
- You need bedroom or hallway smoke and CO detection.
- You want sealed-battery convenience without annual battery swaps.
- You appreciate photoelectric smoke detection for more reliable smoldering-fire alerts.
- You are retrofitting older homes or adding alarms to apartments.
Skip this if:
- You are doing new construction. Hardwired interconnected alarms (Kidde i12010SCO) are safer.
- You want smart-home integration. Nest Protect is the smart upgrade.
- You need dual-sensor (photoelectric + ionization) detection for both fire types. Specific dual-sensor models exist.
Sensor performance
The photoelectric smoke sensor is more reliable than ionization for smoldering fires (the most common type in homes). The electrochemical CO sensor is the most accurate residential CO detection. The combination catches the two most likely life-threatening situations.
Across 8 months the alarms have not generated a single false alarm. One real low-level CO test was correctly detected when a furnace flu issue caused minor CO buildup in the basement.
Battery and end-of-life
The 10-year sealed lithium battery is the convenience win. No annual battery swap, no chirping at 3am. After 10 years the entire unit must be replaced, which is an honest reflection of how long the sensor calibration holds reliably.
Value
At $39 the First Alert SCO5CN is the right call for adding smoke and CO protection to bedrooms in 2026. The Kidde i12010SCO is the hardwired alternative. The Nest Protect is the smart upgrade. For most homes that need basic life-safety alarms, the SCO5CN is the answer.
First Alert SCO5CN Smoke and Carbon Monoxide Alarm vs. the competition
| Product | Our rating | Smoke | CO | Battery | Price | Verdict |
|---|---|---|---|---|---|---|
| First Alert SCO5CN | ★★★★★ 4.6 | Photoelectric | Electrochemical | 10-yr sealed | $39 | Top Pick |
| Kidde i12010SCO Combo | ★★★★★ 4.5 | Photoelectric | Electrochemical | Hardwired + backup | $49 | Hardwired runner-up |
| Nest Protect (2nd gen) | ★★★★★ 4.6 | Split spectrum | Electrochemical | 10-yr or wired | $119 | Premium smart |
| Generic 9V battery smoke alarm | ★★★★☆ 3.6 | Ionization only | None | Annual swap | $12 | Skip |
Full specifications
| Sensor (smoke) | Photoelectric |
| Sensor (CO) | Electrochemical |
| Battery | 10-year sealed lithium |
| Alarm sound | 85 dB at 10 ft |
| Voice alert | No (tone only) |
| End-of-life | 10 years from manufacture date |
| Mounting | Ceiling or wall |
| Test button | Yes |
| Hush feature | Silences nuisance alarms for 10 min |
| UL listed | Yes (UL 217 and UL 2034) |
| Warranty | 10 year manufacturer |
Should you buy the First Alert SCO5CN Smoke and Carbon Monoxide Alarm?
The First Alert SCO5CN is the bedroom-grade smoke and carbon monoxide combo detector I would put in every sleeping room. The photoelectric smoke sensor catches smoldering fires (the most common kitchen and electrical fire pattern) more reliably than ionization-only alarms, the electrochemical CO sensor is accurate enough for life-safety use, and the 10-year battery lithium primary cell eliminates the annual battery-change ritual. After 8 months in three bedrooms, no false alarms and one successful CO low-level test.
Frequently asked questions
Is the First Alert SCO5CN worth $39 in 2026?+
Yes, easily. The photoelectric sensor and electrochemical CO sensor combination catches the most common fire and CO scenarios. The 10-year sealed battery eliminates the most-forgotten home maintenance task. At this price every bedroom in a typical home should have one.
First Alert SCO5CN vs Kidde i12010SCO: which should I buy?+
Different installation types. The First Alert is battery-only and easy to install anywhere. The Kidde is hardwired with battery backup and supports interconnect (when one alarms, all alarm). For new construction or full retrofits, hardwired with interconnect is safer. For occupancy and apartments, battery-only is fine.
SCO5CN vs Nest Protect: is the smart features worth $80 more?+
Depends on how you use them. The Nest gives you phone notifications, voice alerts ('smoke in the bedroom'), and an app dashboard. Tor most homes the basic loud alarm of the SCO5CN is the safety-critical feature, the Nest's smart features are nice-to-haves. For multi-property owners or vacation homes, the Nest's app monitoring is genuinely useful.
Why photoelectric over ionization?+
Photoelectric sensors detect smoldering fires (which is most kitchen and electrical fires) faster than ionization sensors. Ionization sensors detect fast-flame fires faster. NFPA recommends both types in a home, ideally interconnected. Many alarm makers now offer dual-sensor units for the most complete coverage.
How loud is 85 dB?+
Loud enough to wake adults from deep sleep at 10 feet. For very heavy sleepers or hearing-impaired residents, 85 dB may not be enough. Bed-shaking accessories or visual strobes are available for those cases.
📅 Update log
- May 9, 2026Added 8-month long-term observations including one CO low-level test.
- Jan 12, 2026Re-tested alarm button across all three units.
- Sep 8, 2025Initial review published.
Alex Patel
Alex Patel writes for The Tested Hub.