Best Smart Carbon Monoxide Detector in 2026
Carbon monoxide (CO) is an odorless, colorless gas produced by fuel-burning appliances — gas furnaces, water heaters, fireplaces, generators, and cars. Standard CO detectors alarm only when CO reaches dangerous levels. Smart detectors alert your phone when CO is elevated, even at sub-alarm levels, giving earlier warning when the source can still be safely addressed.
What Smart Adds to CO Detection
Remote alerts: Notification to your phone when CO is detected — critical for vacation properties, second homes, or when everyone in the household is asleep and a traditional alarm might not wake them in time.
CO level visibility: Smart detectors show current CO PPM (parts per million) levels in the app. Early elevated readings (below alarm threshold) can prompt investigation before CO reaches dangerous concentrations.
Interconnected alerts: All smart detectors in the home alert simultaneously when one detects CO.
Integration: Trigger smart home automations — turn on fans, unlock doors, call for help.
CO Safety Reference
| CO Level (PPM) | Effect at 8-hour exposure |
|---|---|
| 35 PPM | Headache and dizziness with long exposure |
| 200 PPM | Headache, dizziness, disorientation within 2-3 hours |
| 400 PPM | Life-threatening within 3 hours |
| 800 PPM | Death within 3 hours |
| 1,600 PPM | Death within 1 hour |
NFPA (National Fire Protection Association) requires CO detectors in all sleeping areas and on every level of the home.
Top Picks
Best Combo: Google Nest Protect (Smoke + CO)
Price: ~$120 | Best for: Combined smoke + CO, Steam Check, phone alerts**
Nest Protect detects both smoke and carbon monoxide in one device — eliminating the need for separate units on each level. Sends phone alerts via the Nest app for both smoke and CO events. Shows CO levels in the app. "Heads Up" pre-alarm at lower CO concentrations gives early warning before the full alarm activates.
At $120 per unit, buying Nest Protect for every required location (one per level, one per sleeping area) is expensive in larger homes. But the combination of smoke + CO detection in one premium unit reduces the total device count.
Pros: Smoke + CO combined, phone alerts for both, CO PPM in app, Steam Check (fewer false smoke alarms), 10-year sensor
Cons: $120/unit, expensive for multi-unit installations, Google account required
Budget Pick: First Alert CO605 WiFi CO Detector
Price: ~$60 | Best for: Budget CO-only smart detector, phone alerts**
First Alert's WiFi CO detector sends push notifications when CO is detected and shows current PPM level in the First Alert app. CO-only (no smoke detection — pair with a smoke detector on the same unit or a separate smoke alarm). 7-year sensor life. At $60, it provides the core smart CO feature (phone alert) at half the price of Nest Protect.
Pros: $60, WiFi phone alerts, CO PPM display in app, 7-year sensor, no hub required
Cons: CO only (no smoke), First Alert app is basic, no Google/Alexa integration
Best for Existing Systems: Kidde Carbon Monoxide Detector with WiFi
Price: ~$50 | Best for: Plug-in, simple, WiFi alerts**
Kidde's plug-in WiFi CO alarm plugs directly into a wall outlet (no installation required) and sends phone alerts via the RemoteLync app. Ideal for renters who cannot install hardwired detectors, or for adding CO monitoring to specific areas quickly.
Pros: $50, plug-in (no installation), WiFi alerts, portable, no hub
Cons: Plug takes an outlet, CO only, basic app, no Alexa/Google integration
Comparison Table
| Detector | Price | Detection | Phone Alerts | Sensor Life | Hub |
|---|---|---|---|---|---|
| Nest Protect | ~$120 | Smoke + CO | Yes | 10 years | No |
| First Alert CO605 | ~$60 | CO only | Yes | 7 years | No |
| Kidde WiFi | ~$50 | CO only | Yes | 7 years | No |
Frequently Asked Questions
Where should CO detectors be placed?
NFPA 720 requires CO detectors on every level of the home and within 10 feet of each sleeping area. For fuel-burning appliances, placement near the appliance provides earlier detection.
Do CO detectors expire?
Yes — electrochemical CO sensors degrade over time. Most detectors have a 5-10 year sensor life. The detector should beep intermittently at end-of-sensor-life, and the packaging/back label indicates the replacement date.
Can I use one smart smoke/CO detector instead of separate units?
Combined detectors (Nest Protect, First Alert Onelink) are efficient — one unit per location instead of two. They cost more per unit but simplify installation and reduce total device count in smaller homes. In larger homes requiring many units, budget CO-only or smoke-only detectors at each location may be cost-effective.