Head-to-head · Best Carbon Monoxide Detectors

First Alert SC5 Smart Smoke and Carbon Monoxide Alarm vs Klein Tools ET110 CO Meter

Which is the better buy? Side-by-side on rating, price, strengths, and watch-outs — with the published ratings we averaged to get there.

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The short answer

First Alert SC5 Smart Smoke and Carbon Monoxide Alarm comes out ahead by a clear margin (4.5 vs 4.0). The gap is mostly about Smart home users wanting integration — read the strengths below before deciding.

Higher ratedRanked #2 in Best Carbon Monoxide Detectors

First Alert SC5 Smart Smoke and Carbon Monoxide Alarm

4.5

2 sources1 derived$129.96as of Aug 1

The First Alert SC5 Smart Smoke and Carbon Monoxide Alarm wraps app-based control in a modern design that adds up to better home safety. Bob Vila reviewers liked the simple installation, the one-button silence feature, and Google Home integration. Isaac from Smart Home Explained rated the build quality above the competition and found app setup smooth. Against that: the $130 price point and interconnect features that only work with a limited set of brands. It suits people who want smart home integration and a better user experience than traditional detectors give, though anyone with existing non-First Alert systems won't get full network coverage.

Strengths

— Easy installation with pre-installed batteries and voice-guided setup
— One-button silence feature improves user experience during false alarms
— Integrates seamlessly with Google Home smart home ecosystem

Watch-outs

— Price is significantly higher than standard alarms at around $130 per unit
— Limited interconnect compatibility with other brands like Kidde and Nest Protect

$129.96 · Check Price on Amazon Full review →

Ranked #3 in Best Carbon Monoxide Detectors

Klein Tools ET110 CO Meter

4.0

2 sourcesall derived$129.99as of Aug 1

The Klein Tools ET110 is a handheld carbon monoxide meter built for HVAC technicians checking for unsafe CO levels. Reviewers pointed to the dual-color indicator light, the audible and visual alarms, and a backlit display with large digits that stays readable. It zero-calibrates automatically at power-on, runs a 3-minute diagnostic self-test, and carries a 5-year expected sensor lifetime. The range runs 0 to 1000 ppm at 1 ppm resolution, with temperature measurements included. Reviewers did flag limited humidity tolerance and a narrow storage temperature range, which could affect usability in extreme climates.

Strengths

— Backlit monochrome LCD display with large digits for clear readings
— Audible and visual alarms at 35 ppm and 200 ppm levels
— Auto power-off after 20 minutes of inactivity for battery savings

Watch-outs

— RH limit of <85% may present problems in very humid climates
— Storage temperature range only 23°F to 131°F (-5°C to 55°C)

$129.99 · Check Price on Amazon Full review →

Derived means the reviewer published no score, so one was inferred from their written verdict. Everything else is a number the publisher printed. How we rank.

How they stack up

First Alert SC5 Smart Smoke and Carbon Monoxide Alarm

The SC5 Smart Alarm outperforms the CO710 in smart home integration with Google Home compatibility and app-based testing, while the CO710 lacks smart connectivity. Compared to the basic First Alert detector, the SC5 offers superior user experience with one-button silence and voice alerts, though it comes at a significantly higher price point.

Klein Tools ET110 CO Meter

Unlike the First Alert models, the Klein Tools ET110 offers professional-grade accuracy with 1 ppm resolution and a 5-year sensor lifetime, making it superior for HVAC technicians who need precise readings. While the First Alert SC5 provides smart home integration and the CO710 has a sealed 10-year battery, the Klein model stands out with its auto zero-calibration and 3-minute diagnostic self-test, features not found in the other handheld detectors.

Specs side-by-side

Spec	First Alert SC5 Smart Smoke and Carbon Monoxide Alarm	Klein Tools ET110 CO Meter
Detection Type	Smart Smoke and CO Alarm	Carbon Monoxide
Power Source	Built-in lithium backup battery	4 x AAA batteries
Battery Life	10-year sealed lithium battery	—
Connectivity	Google Home compatible	None
Display	LED light ring	Backlit monochrome LCD
Features	App-based testing, voice alerts, one-button silence	Audible and visual alarms, Backlit LCD, Auto-Power Off
Dimensions	5.75"D x 1.6"W x 5.75"H	7.74"D x 2.16"W x 1.46"H
Material	—	Blend

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