First Alert SMICO100-AC

Detects both smoke and CO in one device

Quick Connect plug — easy installation, no rewiring needed

Battery backup — keeps running during power outages

End-of-life warning — tells you when it's time to replace

Low battery alert — no surprise midnight chirping

Optional locking feature — prevents accidental removal

False alarms — Many nuisance alerts

Requires hardwiring — not a simple plug-in, you'll likely need an electrician

No digital display — no way to see actual CO levels in real time

CO only detection threshold unknown — no indication of when it starts monitoring

Does NOT detect propane and natural gas

Overall Score

8.4

VISIT SITE

$50

1-3 Days Express Shipping

Kidde Smoke and Carbon Monoxide Detector

2-in-1 detection — catches both smoke and carbon monoxide in one device

High decibel alarm — loud enough to wake the whole house, with red LED visual alert

Hardwired with battery backup — runs on 120V AC power, batteries kick in if power goes out

10-year warranty — one of the longest coverage periods on the market

Beeping issues — Repeatedly malfunction and chirp in the middle of the night

False alarms — Many nuisance alerts

Does NOT detect propane and natural gas

CO only detection threshold unknown — no indication of when it starts monitoring

No digital display — no way to see actual CO levels in real time

Requires hardwiring — not a simple plug-in, you'll likely need an electrician

Overall Score

8.2

VISIT SITE

$55

1-3 Days Express Shipping

First Alert CO615

Plug-in with battery backup — works in any standard outlet, keeps monitoring even during power outages

Live digital display — shows real-time CO levels at all times

Peak level memory — records the highest CO concentration detected, useful for tracking exposure

High decibel alarm — loud enough to alert the whole household when danger hits

End-of-life alert — chirps when it's time to replace so you're never unknowingly unprotected

Display hard to read — indicator light deeply recessed, requiring you to fully bend down to see it

Questionable accuracy — we left it in a previously CO-contaminated environment for 3 hours and it never read above 0

Doesn't show true real-time readings — it doesn't display live continuous CO levels

Press-to-test only tests the alarm sound — not the actual sensor, giving false confidence the device is working

Does NOT detect propane and natural gas

Overall Score

7.6

VISIT SITE

$36

1-3 Days Express Shipping

First Alert and Kidde are no longer the first choice for many new homeowners in 2026.

 

If you have kids, elderly parents, or pets, and you're looking for better protection, then we recommend this instead:

 

>> you can click this text here <<

(It's a plug-in type)