The Best Smart Smoke & Carbon Monoxide Detectors: 4 Compared (and One to Skip)

RBE top pick

First Alert SC5 Smart Smoke & Carbon Monoxide Alarm

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The First Alert SC5 is the most complete smart smoke-and-CO alarm for most homes, especially if you use the Google Home app, and it comes in both battery and hardwired versions. The X-Sense XP0A-iR is the value runner-up: standalone Wi-Fi with voice alerts and phone notifications, with no hub to buy.

A smart smoke and carbon-monoxide alarm still has one job that matters most: make noise the instant there is a fire or CO leak, whether or not your phone is nearby. The 'smart' part - app alerts that tell you which room, silence-from-phone, and links to the rest of your home - is a genuine upgrade, but only if the core detection is solid. We lined up four alarms you can actually buy in 2026: two we would happily mount today, one that fits a specific kind of home, and one that looks tempting but leaves a dangerous gap.

RBE top pick

First Alert

First Alert SC5 Smart Smoke & Carbon Monoxide Alarm

Buy it

The de facto successor to the old Google smart alarm, with phone alerts and Google Home compatibility.

Best for: Anyone already running a Google/Nest home who wants smart alerts that work with Google Home.

$$$ · premium

Why we like it

• Detects both smoke and carbon monoxide and works with the First Alert app and the Google Home app, with voice alerts that name the danger and location
• Sold in both battery and hardwired versions, so it fits renters and wired homes
• Interconnects with compatible alarms, sends phone alerts, and uses voice alerts with a heads-up warning

Know before buying

• You are buying into the Google Home ecosystem - the best features assume you use that app
• Premium price, especially once you cover a whole house

Check price on Amazon Read our detailed assessment ↓

X-Sense

X-Sense XP0A-iR Wi-Fi Smart Smoke & Carbon Monoxide Alarm

Buy it

Standalone Wi-Fi with voice alerts and phone notifications - the value pick that needs no hub.

Best for: Value hunters and non-ecosystem homes that want app alerts without buying into a smart-home platform.

$$ · mid-range

Why we like it

• Connects to Wi-Fi and pushes phone alerts on its own - no separate base station or bridge required
• Photoelectric smoke sensor and electrochemical CO sensor, with a voice alarm that announces the type of hazard
• Replaceable battery keeps maintenance simple

Know before buying

• Lives in X-Sense's own app rather than plugging into Google Home or Alexa routines
• 2.4 GHz Wi-Fi only, and the brand has less name recognition than First Alert or Kidde
• X-Sense's own page contradicts itself on interconnection, so confirm with X-Sense before counting on linked alarms

Find it on Amazon Read our detailed assessment ↓

Kidde

Kidde Smoke + Carbon Monoxide Alarm with Smart Features (P4010ACSCO-WF)

It depends

A hardwired smart combo that works with existing Kidde interconnected alarms - great if you have the wiring and patience for the app.

Best for: Owners of wired homes who want a set-and-forget, whole-home interconnected system and don't mind the app.

$$$ · premium

Why we like it

• Hardwired, so it draws house power rather than relying on a battery alone
• Designed to work with existing Kidde hardwire interconnected alarms so they all sound together, plus Wi-Fi phone alerts through the Kidde app
• Widely stocked and easy to find replacements and support for

Know before buying

• Hardwired install means existing wiring or an electrician - not a renter-friendly, peel-and-stick job
• Owner reports flag a fiddly setup and less-polished app than the competition; Kidde publishes product safety notices, so check the current model's notices before you buy

Find it on Amazon Read our detailed assessment ↓

We'd skip it

Heiman

Heiman Matter Smart Smoke Alarm (HS2SA)

Skip it

Cheap and compact, but it only detects smoke - leaving the carbon-monoxide half of the job undone.

Best for: Almost no one shopping for smoke-and-CO protection; at most a supplement where CO is already covered.

$ · budget

Why we like it

• Inexpensive and compact
• Maker lists Zigbee and Wi-Fi wireless options across the HS2SA series

Know before buying

• Detects smoke only - it does not sense carbon monoxide at all, so it fails the core 'smoke and CO' brief
• You would still need to buy separate CO alarms, and support for the lesser-known brand is thin

See our pick instead Find it on Amazon anyway Read our detailed assessment ↓

How we judged the field

We don’t run a fire lab, and we don’t pretend to. Instead we synthesize maker specifications and a large pool of owner reports, then weigh it against the one thing that actually saves lives: reliable, loud detection of both smoke and carbon monoxide. The ‘smart’ layer is a real convenience - but it only earns points once the fundamentals are covered.

The criteria that mattered most: does it detect both smoke and CO, or just one; how trustworthy and false-alarm-resistant the sensing is according to maker specs and owner reports; how the phone alerts behave (do they name the room, can you silence from your phone); how it installs (peel-and-stick battery versus house wiring); whether units interconnect so they all sound together; and lifespan before you must replace the whole unit. Price we treat only in qualitative tiers, because what you really care about is value for whole-home coverage.

This is the alarm most people should start with. It detects smoke and carbon monoxide and connects to the Google Home app, where the maker highlights phone alerts, interconnect with compatible alarms, and voice alerts that name the type and location of the danger. Owners like that it comes in both a battery model (simple to mount anywhere) and a hardwired model (for homes with existing wiring). The trade-off is ecosystem gravity: you get the most out of it inside a Google/Nest household, and it sits at a premium price once you cover several rooms. For the target buyer, that’s a fair deal for the most complete package here.

The X-Sense is the value story of this group and, for a lot of homes, the smarter buy. It connects straight to Wi-Fi with no separate hub or bridge, pushes alerts to your phone, and a built-in voice alarm announces the type of hazard. Combined with a replaceable battery, it keeps maintenance simple. The caveats: X-Sense’s page lists ‘Interconnected Alarm’ among this model’s features while its site menu files it under ‘No Alarm Interconnection’, so confirm with X-Sense before you plan on alarms sounding together; everything runs through X-Sense’s own app rather than folding into Google Home or Alexa routines, it uses 2.4 GHz Wi-Fi only, and the brand carries less household recognition than the legacy names. None of that undercuts the core protection, which is why it lands as a confident buy.

Kidde’s smart combo is hardware aimed at a specific home. It’s hardwired and designed to work with existing Kidde hardwire interconnected alarms, so a threat in one room sets off all of them, plus Wi-Fi phone alerts through the Kidde app. The reasons it’s an ‘it depends’ rather than a straight buy: the hardwired install assumes you already have alarm wiring (or will pay an electrician), which rules out most renters, and owner reports describe a fussier setup and a less-refined app than rivals. Kidde publishes product safety notices, so it’s worth a quick check of the current model’s notices before purchase. If you own a wired home and want a set-and-forget interconnected system, it’s a reasonable pick; if not, one of the buys above is easier to live with.

On paper the Heiman looks appealing: it’s inexpensive, compact, and the maker offers Zigbee and Wi-Fi wireless options across the series. The problem is the one that matters. It detects smoke only - it does not sense carbon monoxide at all. In a roundup about smoke and CO protection, that’s a disqualifying gap, because CO is the invisible, odorless threat you most need a device to catch. Buying it and assuming you’re covered would leave you exposed, and you’d still have to purchase separate CO alarms. Combined with thin support for the lesser-known brand, it’s the one to skip for this purpose; at best it’s a supplement in a home where CO is already handled by proper combo alarms.

First Alert SC5 vs X-Sense XP0A-iR: which should you buy?

Both detect smoke and CO, both send phone alerts, and both are easy to recommend - the deciding factor is your home. Choose the First Alert SC5 if you live in the Google/Nest world and want the most polished smart experience: phone alerts, voice alerts, and interconnect with compatible alarms, with Google Home compatibility. It also gives you a hardwired path if you want alarms tied into house power. Choose the X-Sense XP0A-iR if you’d rather not adopt a platform at all: it stands alone on Wi-Fi, announces the hazard by voice, and needs no platform. Put simply - SC5 for ecosystem polish, XP0A-iR for value and independence. Neither is a wrong answer.

What to look for

• Both sensors, always. For this category, insist on combined smoke and carbon-monoxide detection; a smart smoke-only alarm leaves the most dangerous gap.
• How it installs. Battery and standalone-Wi-Fi models suit renters and quick coverage; hardwired models suit wired homes that want always-on power and code-style interconnect.
• Useful alerts. The best systems name the room and let you silence a nuisance alarm from your phone - far more valuable than a generic ‘alarm sounding’ ping.
• Interconnection. If one alarm trips, do the rest sound too? Whole-home linking (wired or wireless) buys you critical seconds.
• Lifespan and power. Check the replace-by date and whether the battery is replaceable or sealed for the life of the unit.
• Local rules first. Confirm what your local code requires before relying on any alarm; smart features don’t override those requirements.

Our final take

Start with the First Alert SC5: it’s the most complete smart smoke-and-CO alarm for most homes, it plays nicely with the Google Home app, and the choice of battery or hardwired versions means almost anyone can fit it. If you want the same dual protection for less and don’t care about a smart-home platform, the X-Sense XP0A-iR is the value pick that punches above its tier with a standalone Wi-Fi setup, voice alerts and phone notifications. Reserve the Kidde smart combo for wired homes that specifically want an always-powered, interconnected system and can tolerate a rougher app. And whatever you do, don’t let the cheap, smart-looking Heiman fool you - a smoke-only alarm is no substitute for real carbon-monoxide protection. Buy the right alarm for how your home is wired, mount enough of them, test monthly, and replace them on schedule.

Deciding between the top two? See our head-to-head: First Alert SC5 Smart Smoke & Carbon Monoxide Alarm vs X-Sense XP0A-iR Wi-Fi Smart Smoke & Carbon Monoxide Alarm.

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