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.

The short answer

Klein Tools ET110 CO Meter comes out ahead by a narrow margin (4.1 vs 4.2). The gap is mostly about HVAC technicians needing precision — read the strengths below before deciding.

Ranked #4 in Best Carbon Monoxide Detectors

First Alert SC5 Smart Smoke and Carbon Monoxide Alarm

4.1

$111

The First Alert SC5 Smart Smoke and Carbon Monoxide Alarm offers a modern design and app-based control that enhances home safety. Bob Vila reviewers praised its simple installation, one-button silence feature, and Google Home integration. Isaac from Smart Home Explained noted the device's superior build quality and smooth app setup process. However, the $130 price point and limited brand compatibility for interconnect features are drawbacks. This alarm suits users seeking smart home integration and improved user experience over traditional detectors, but those with existing non-First Alert systems may miss out on 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

$111 · Check Price on Amazon Full review →

Higher ratedRanked #3 in Best Carbon Monoxide Detectors

Klein Tools ET110 CO Meter

4.2

$204

The Klein Tools ET110 is a handheld carbon monoxide meter designed for HVAC technicians to detect unsafe CO levels. Reviewers noted its dual-color indicator light, audible and visual alarms, and backlit display with large digits for clear readings. The device features automatic zero-calibration at power-on, a 3-minute diagnostic self-test, and a 5-year expected sensor lifetime. It measures CO from 0 to 1000 ppm with 1 ppm resolution and includes temperature measurements. However, some reviewers pointed out its limited humidity tolerance and narrow storage temperature range, which may 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)

$204 · Check Price on Amazon Full review →

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	—
Display	LED light ring	Backlit monochrome LCD
Alarm Thresholds	70 PPM CO concentration	35 ppm and 200 ppm levels
Features	App-based testing, voice alerts, one-button silence	Audible and visual alarms, Backlit LCD, Auto-Power Off

← See the full ranking of best carbon monoxide detectors