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An independent comparison of the best smoke and carbon monoxide detectors to protect your home from fire
Have a pro fit interconnected alarms or a full alert system to NFPA 72 placement.
Free quoteEach detector was assessed against safety standards and in real-world conditions. We evaluate:
| Detector | Rating | Price | Type | Best for | Action |
|---|---|---|---|---|---|
| Google Nest Protect | 4.8/5 | $$$ | Smart smoke + CO | Complete protection | Amazon → |
| X-Sense Smart Smoke Alarm | 4.5/5 | $$ | Smart smoke | Value smart pick | Amazon → |
| Kidde Firex | 4.5/5 | $ | Standalone (UL 217) | Budget, reliability | Amazon → |
| First Alert CO Detector | 4.4/5 | $ | Carbon monoxide (UL 2034) | Furnace, stove, fireplace | Amazon → |
The most complete protection. A combination smoke and carbon monoxide alarm that talks to your phone, interconnects across levels and uses a split-spectrum sensor to cut nuisance alarms.
Multi-story homes and households that want one device covering smoke and CO, with remote alerts and whole-home interconnection.
Indicative price. Verify current offers.
Smart alerts without the premium price. A UL 217 listed photoelectric alarm with a 10-year sealed battery, smartphone notifications and an interconnectable base.
Family apartments and homes where you want remote alerts and interconnection without paying flagship money.
The reliable, code-compliant workhorse. A UL 217 listed alarm that hardwires and interconnects with other Kidde units — simple, proven and inexpensive.
Rating: 4.4/5 | Price: $30–60
A dedicated, UL 2034 listed carbon monoxide alarm for any home with a furnace, gas stove, fireplace or attached garage. A smoke alarm does not detect CO — if you burn any fuel, add one of these. Combination smoke/CO models are also available if you'd rather have a single device.
View on Amazon→ Our pick: Google Nest Protect (~$129)
Smoke + CO, smartphone alerts and whole-home interconnection in one device.
→ Our pick: X-Sense Smart Smoke Alarm (~$100)
Affordable smart alerts and interconnection, with a 10-year sealed battery.
→ Our pick: Kidde Firex (~$49)
A UL 217 listed standalone that interconnects — proven and inexpensive.
→ Add: a First Alert CO detector ($30–60, UL 2034)
Carbon monoxide is odorless and deadly — a smoke alarm can't see it.
If you had to pick one regardless of budget: the Google Nest Protect. It detects both smoke and carbon monoxide, alerts your phone, and interconnects across levels. For a tight budget, the Kidde Firex is a reliable UL 217 listed standalone; for an affordable smart option, the X-Sense Smart Smoke Alarm; and for dedicated CO coverage near a furnace or stove, a UL 2034 listed First Alert CO detector.
Both, because they detect different dangers. A smoke alarm (UL 217 listed) detects a fire; a carbon monoxide detector (UL 2034 listed) detects a deadly, odorless gas produced by faulty combustion (furnace, stove, fireplace, water heater). CO detectors are required in many states wherever there's a fuel-burning appliance. Combination units like the Nest Protect cover both in one device.
Per NFPA 72: one in every bedroom, one outside each sleeping area, and one on every level of the home (including the basement). For a multi-story or larger house, add one in each nighttime hallway. Interconnected models all sound together, which is essential across multiple levels.
A standalone UL 217 listed alarm with a 10-year sealed battery is enough for a small home where you're usually present. A smart or interconnected alarm earns its price if you're often away (smartphone alerts, can notify a family member) or in a multi-story house (all alarms sound together).
About 10 years. After that, the sensing element loses reliability — replace the unit even if it still seems to work. Sealed-battery models last ~10 years with no battery change; models with a removable battery need a yearly replacement. Test every alarm once a month and dust them regularly.
To go beyond this comparison, these resources help you choose, place and maintain your alarms.
