Head-to-head · Best Carbon Monoxide Detectors

Kidde Hardwired Smart Smoke and Carbon Monoxide Detector 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

Kidde Hardwired Smart Smoke and Carbon Monoxide Detector comes out ahead by a narrow margin (4.4 vs 4.2). The gap is mostly about Users prioritizing traditional safety — read the strengths below before deciding.

Higher ratedRanked #2 in Best Carbon Monoxide Detectors

Kidde Hardwired Smart Smoke and Carbon Monoxide Detector

4.4

$75

The Kidde Hardwired Smart Smoke and Carbon Monoxide Detector offers comprehensive safety with a 10-year battery life and advanced detection technology that's 25% faster and 3X more precise than average smoke alarms. TechHive reviewer Christopher Null praised its reliable performance and interconnect capabilities but noted it lacks smart home integration and is pricey for a non-smart model. The unit includes voice alerts and can interconnect up to 24 devices, though installation requires basic wiring knowledge. Best for users prioritizing traditional safety features over smart connectivity.

Strengths

— 10-year lifespan with non-removable battery
— Fast smoke detection (25% faster than average)
— 3X more precise smoke detection than average

Watch-outs

— No smart home connectivity or Wi-Fi features
— Busy design that juts out 2 inches from wall/ceiling
— High price for model without smart features

$75 · Check Price on Amazon Full review →

Ranked #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

Kidde Hardwired Smart Smoke and Carbon Monoxide Detector

The Kidde hardwired model surpasses the SC5 in detection speed and precision, offering 25% faster smoke detection and 3X more accurate readings, while the SC5 lacks these performance advantages. Unlike the basic First Alert detector, it provides advanced interconnect features for up to 24 devices, though it lacks smart home integration. The Klein ET110 offers more professional-grade features, but the Kidde model provides the most robust traditional safety features.

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	Kidde Hardwired Smart Smoke and Carbon Monoxide Detector	Klein Tools ET110 CO Meter
Detection Type	Dual Sensor	Carbon Monoxide
Power Source	Hardwired	4 x AAA batteries
Battery Life	10 years	—
Connectivity	Wi-Fi, Ring App, Amazon Alexa, Google Home	—
Display	LED indicator	Backlit monochrome LCD
Features	Voice alerts, false alarm reduction	Audible and visual alarms, Backlit LCD, Auto-Power Off
Alarm Thresholds	—	35 ppm and 200 ppm levels

← See the full ranking of best carbon monoxide detectors