The First Alert SC5 is a battery-powered combination smoke and carbon monoxide alarm, measuring 5.75 x 5.75 x 1.6 inches, with an electrochemical CO sensor, a photoelectric smoke sensor and Google Home connectivity. CNET named it the best overall carbon monoxide detector in its lab-tested roundup, citing accurate sensors, phone alerts through Google Home and voice alerts that state what the alarm is sensing. Bob Vila rated it 4.5/5, reporting a three-minute setup with preinstalled batteries and a large centre button that silences cooking false alarms. It suits Google Home households that want smoke and CO coverage in places without wiring; homes where codes require hardwired alarms, or buyers fitting many rooms on a tight budget, should look elsewhere.
Full review
Lab-tested sensors with alerts on the phone
CNET chose the SC5 as its best overall carbon monoxide detector after running detectors through a custom test rig that timed responses at 250 ppm and 400 ppm concentrations. The publication credits First Alert with accurate sensors and pairs that with Google Home support, which arrives through Nest Protect integration. That link lets the alarm send alerts to a phone wherever the owner is, along with status updates. For households that skip the app, CNET notes the unit still speaks voice alerts that say whether it is detecting smoke or carbon monoxide, and it sounds a siren as well.
Three-minute setup and a one-press silence button
Bob Vila found installation simple: the batteries were preinstalled, so setup meant pulling the battery tab and pairing the alarm in the First Alert app, which took about three minutes from opening the box. Voice prompts from the built-in speaker guide the process, and the test routine gives a five-second spoken countdown before the siren sounds. The reviewer singled out the large central button as the feature used most, silencing alarms set off while cooking with a single press. The square, flat housing is noticeably larger than a traditional detector, though Bob Vila felt it blends in with other ceiling and wall fixtures.
Battery power cuts both ways
Running on batteries means the SC5 can go wherever carbon monoxide is a concern, including garages or sheds with no outlets, which CNET counts in its favour. The same design is its main limitation: CNET warns that a battery-only alarm may not comply with every building code, since some jurisdictions require wired alarms with battery backup in certain locations. Buyers should check local requirements before relying on it as a primary alarm. Price is the other drawback. Bob Vila calls it significantly more expensive than standard alarms, a cost that multiplies when outfitting an entire house, while still judging the control and integration worthwhile in key rooms.
Strengths
- +Detects smoke and carbon monoxide in one unit, with voice alerts that say which hazard it senses
- +Links to the Google Home app via Nest Protect integration for phone alerts away from home
- +CNET named it best overall CO detector after lab tests of its sensors
- +Batteries come preinstalled; Bob Vila went from box to live in the app in about three minutes
- +Large centre button silences nuisance cooking alarms with one press
Watch-outs
- −Battery-only power may not satisfy building codes that require a wired alarm
- −Costs far more than standard alarms, which adds up when equipping a whole house
How it compares
Like the Kidde Smart Smoke + Carbon Monoxide Alarm and the X-Sense SC07-WX, the SC5 combines smoke and CO detection with app alerts, but it runs on batteries and works through Google Home. At around $125 it costs more than a single-purpose unit such as the Kidde Battery-Operated Carbon Monoxide Alarm, which covers carbon monoxide only.
Rating sources
Not in the average — we derived this score from the review's words, and a publisher printed a score for this product, so the printed number counts instead.
Counts as 4.18/5 in our score — this publisher's 42 scores on the site average 4.53, so its scores are adjusted down to compare fairly with other publishers.
“First Alert SC5 Smart Smoke and Carbon Monoxide Alarm Rating: 4.5/5”
Our 4.2 score is the average of 1 of the scored reviews above, each adjusted for how strictly its publisher scores. 1 derived score above is not in the average because a publisher printed a score for this product. Ratings marked * were derived from the reviewer’s written analysis or video transcript — the publisher didn’t print an explicit numeric score, so we inferred one from their own words. Click through to verify. More about methodology.
