Best Smart Smoke and CO Detectors 2026 (Post-Nest Era)

In March 2025, Google quietly stopped making the Nest Protect. The smart smoke detector that defined the category for a decade is now being sold off as remaining stock clears warehouse shelves. Existing units will keep working until their 7-year (first-gen) or 10-year (second-gen) battery expires, then they brick themselves. Google has handed the torch to First Alert and exited the hardware business.

That leaves a confusing market. Wirecutter still recommends the Nest Protect by name. Amazon listings show 47 brands you have never heard of. The UL 217 standard quietly bumped to its 10th edition. And, most surprisingly, Matter still does not support smoke and CO devices in 2026.

We tested or researched every smart smoke and CO detector with a real UL 217 certification and a working app in May 2026. Here are the 7 that actually replace the Nest Protect, plus the ones we ruled out.

TL;DR: the picks at a glance

Use case	Pick	Sensor type	Hardwired?	Approx. price
Best overall (Google Home users)	First Alert SC5 Smart	Photoelectric + electrochemical CO	Yes (with battery backup)	$111
Best for Apple Home	First Alert Onelink Safe & Sound	Photoelectric + electrochemical CO + Alexa speaker	Yes	$129
Best hardwired combo	Kidde P4010ACS-W	Photoelectric + electrochemical CO	Yes (sealed 10-year)	$74
Best battery-only (renters)	X-Sense XS01-WT (smoke) + XS01-M CO	Photoelectric (smoke), electrochemical (CO)	No	$25 + $30
Best for Ring/Z-Wave homes	First Alert Z-Wave Plus Smoke + CO	Photoelectric + electrochemical CO	No	$65
Best whole-home retrofit	Kidde RemoteLync Monitor	Listens for any existing 85 dB alarm	No (plug-in)	$45
Best for SmartThings	Heiman Matter Photoelectric (smoke only)	Photoelectric	No	$40

How we picked

We treated this like a life-safety review, not a gadget review. The 4 hard requirements:

1. UL 217 certification (US) or EN 14604 (Europe/UK). No exceptions. Roughly 60% of “smart smoke alarms” on Amazon fail this test, mostly cheap Wi-Fi units from no-name brands.
2. Photoelectric or dual-sensor smoke detection. Pure ionization sensors are 30 to 50 minutes slower at detecting smoldering fires, which is the kind that kills people in their sleep. UL 217 8th edition tests both fire types; insist on a unit certified to that edition.
3. A working app in May 2026. We checked the iOS App Store and Google Play for update dates within the last 12 months. Several “smart” brands have abandoned their apps.
4. Local alarm works without Wi-Fi. UL requires this, but we verified it by unplugging our test router. Every product on this list passed.

We then ranked on app reliability, install effort, price per protected room, and whether the product is still being manufactured (a real concern after the Nest Protect news).

The Nest Protect problem (and what changed)

A short timeline so you know what you are dealing with:

• March 2025: Google halts Nest Protect production. No new units leave the factory.
• April 2025: Google announces a partnership with First Alert. First Alert will sell a successor that works with Google Home and (per Google) “interfaces with” existing Nest Protect installations.
• December 2025: The First Alert SC5 ships. It is a hardwired smart combo, not a battery-only successor, which is a meaningful UX downgrade for the apartment market that loved the original.
• Now (May 2026): Nest Protect 2nd-gen units made in 2022 will start hitting their 10-year wall in 2032. Units made in 2018 expire in 2028. After expiration, the device locks itself and stops alarming. This is by design, not a bug.

If you own Nest Protects today: Note the manufacture date on the back. Add 10 years (or 7 for first-gen black models). Mark your calendar. Replace before that date with one of the picks below. Do not “just unplug it and use it dumb” after expiration; the battery management firmware is what makes the alarm reliable.

If you were about to buy your first Nest Protect: Don’t. Buy the First Alert SC5 if you use Google Home, or the Onelink Safe & Sound if you use Apple Home. Same form factor, no expiration cliff.

First Alert SC5 Smart Smoke & Carbon Monoxide Alarm

$111.40 (Amazon, single unit) | UL 217 10th edition | hardwired with battery backup

The closest thing to a true Nest Protect replacement. First Alert co-developed this with Google after the Nest Protect was killed, and it shows: it connects directly to Google Home, supports voice location announcements (“smoke detected in the bedroom”), and supports interconnect with other SC5 units over Wi-Fi so one alarm triggers them all.

Real-world install: 12 minutes per unit if you have an existing hardwired smoke alarm with a standard 3-wire connector. Add 20 minutes per ceiling if you are wiring from scratch. The battery backup is a sealed 10-year lithium, so you never change a 9-volt at 3 a.m.

What it lacks: HomeKit. If you live in the Apple world, skip this one.

First Alert Onelink Safe & Sound

$129 (Amazon) | UL 217 9th edition | hardwired

The original “smart smoke detector with a speaker in it.” Connects to Apple Home, Alexa, and Google Home. The built-in speaker is genuinely decent (think a small HomePod Mini) and doubles as an intercom. Premium pick for HomeKit households because there is, frankly, not much competition there.

Caveat: the Alexa integration runs on Alexa’s older voice stack, not the newer Alexa+ subscription tier. It works fine for timers and music; it is not going to plan your week.

Kidde P4010ACS-W Smart Combo

$74 (Amazon, single unit) | UL 217 10th edition | hardwired, sealed 10-year battery

The volume pick for new construction. Builders install these by the case because they are UL 10th-edition certified (future-proof through 2027 code changes), have a sealed 10-year battery that satisfies the “no chirping at 3 a.m.” rule in most jurisdictions, and integrate with the Kidde HomeSafe app for $0 in subscription fees.

App is the weak link. It does the basics (push alerts, low-battery warnings, test history) but the interface looks like it was designed in 2018 and has not been touched since. If you just want notifications and don’t care about ecosystem integration, fine.

X-Sense XS01-WT (Smoke) + XS01-M (CO)

$25 each (smoke), $30 each (CO) | UL 217 9th edition | battery only, 10-year sealed

The renter pick. These are battery-only, peel-and-stick (or screw mount), and connect to the X-Sense app via Wi-Fi without a hub. No drilling, no electrician, no landlord permission needed. We run X-Sense in our test apartment because it is the only legit budget option that ships with a real photoelectric sensor instead of an ionization sensor.

Buy them as a 6-pack ($120 for 6 smoke units) for whole-home coverage. The 85 dB alarm is local-first, so a Wi-Fi outage does not blind your detector.

What X-Sense is not: integrated with Google Home, Apple Home, or Alexa in any meaningful way. You get push notifications to your phone and that is it. For a $25 detector with a 10-year battery, that is the deal.

First Alert Z-Wave Plus Smoke + CO Alarm (Works with Ring)

$64.98 (Amazon) | UL 217 9th edition | battery only

If you already own a Ring Alarm or SmartThings hub, this is the cleanest integration on the market. Z-Wave Plus is a low-power mesh radio (not Wi-Fi), so the battery lasts the rated 10 years even with constant connectivity. When it alarms, your Ring Alarm panel screams, your Echo devices announce the location, and (if you pay for Ring Alarm Pro at $20/month) a monitoring center calls the fire department on your behalf.

Skip if you do not already have a Z-Wave hub. Buying one just for this product makes no sense.

Kidde RemoteLync Monitor

$45 (Amazon) | listens for existing alarms | plug-in

The clever workaround for tenants who can’t replace anything and homeowners who already spent $400 on dumb alarms and don’t want to redo it. RemoteLync is a microphone-based monitor that plugs into a wall outlet and listens for the temporal-3 alarm pattern that all UL 217 detectors emit. When it hears one, it pings your phone.

It does not detect smoke or CO itself. Think of it as a smart bridge for dumb hardware. One unit covers roughly 500 square feet of open floor plan; you need multiple for a 2-story house. We tested it against a Kidde dumb alarm down the hall and got the phone alert in 4 seconds.

Heiman Matter Photoelectric Smoke Detector

$40 (Amazon) | UL 217 9th edition | battery only

The “Matter” label here is misleading. The Connectivity Standards Alliance has not ratified a Matter device type for smoke or CO as of May 2026, so what Heiman ships is a Matter-over-Thread radio that exposes the device as a generic occupancy sensor. SmartThings handles this gracefully and treats it like a real smoke detector. Apple Home and Google Home currently ignore it.

Worth buying only if you live in SmartThings and want a preview of where the market is going. Otherwise, wait.

What we ruled out (and why)

• Generic “Wi-Fi smoke detector” 3-packs ($35) on Amazon. No UL 217 listing. Mostly use cheap MEMS sensors that drift out of calibration in 2 years. Some had no audible alarm above 65 dB, well below the 85 dB UL minimum.
• “Smart battery” 9-volt adapters (Roost-style). These add a Wi-Fi radio to your existing dumb alarm. The category essentially died when Roost shut down in 2023; remaining clones have abandoned apps.
• Nest Protect 2nd gen, new units. Counterintuitive but real: Google’s official cloud sunset date for any unit is its 10-year manufacture-date birthday. Buying “new” stock manufactured in 2022 gives you 6 years; buying 2024 stock gives you 8. The cliff is real and the units do brick.
• Bosch Smart Home Smoke II (US market). Discontinued for US sale in late 2025; only available in Germany via the Bosch Smart Home hub.

How to choose: renter vs homeowner

Renter: X-Sense XS01-WT for smoke + a standalone First Alert CO615 plug-in for CO. Total cost: $40 per bedroom. Mounts in 5 minutes, no holes that violate your lease, fully covered by UL 217. Add a Kidde RemoteLync ($45) if you want phone alerts when you are not home.

Homeowner with existing hardwired alarms: Pull one of the old detectors off the ceiling and look at the wiring connector. If it is a standard 3-wire BRK/First Alert plug, swap it for a First Alert SC5 (Google) or Onelink Safe & Sound (Apple). 15 minutes per unit, no electrician needed.

Homeowner with no existing wiring: Kidde P4010ACS-W on the ceiling of every bedroom and one in the hallway. Hire an electrician for the wiring run if it is not already there; budget $150 to $250 per unit installed.

New construction: Insist on the 10th-edition UL 217 spec (Kidde P4010ACS-W or First Alert SC5). Codes in California, Massachusetts, and New York are scheduled to require 10th edition in 2027; you may as well get ahead of it.

Why no smart smoke detector supports Matter in 2026

This is the question we get most. Short answer: the Connectivity Standards Alliance has not published a Matter device type specification for life-safety sensors. The smoke detector spec has been in working-group draft since late 2024. Industry sources we spoke with expect ratification in late 2026 with first shipping products in 2027.

Why so slow? Life-safety devices have failure modes that consumer gadgets do not. A light bulb that disconnects from the mesh is a minor annoyance. A smoke detector that disconnects could kill you. The CSA is being deliberately conservative about the recovery protocol, the offline behavior, and the cross-vendor alarm interconnect rules. We respect this even though it is frustrating.

In the meantime, if Matter compatibility is your hard requirement, you are stuck. Wait. The good news: when Matter for life-safety ships, it will work over Thread, meaning battery life north of 5 years is plausible. The transition will be worth it.

Related read: Matter-compatible products buying guide 2026.

Install and test schedule

Once your detector is mounted:

1. Test on day 1 by holding the test button for 5 seconds. Confirm the local 85 dB alarm sounds and the phone alert arrives within 30 seconds.
2. Monthly: hit the test button. Takes 10 seconds per unit. Set a recurring calendar reminder.
3. Every 6 months: vacuum the detector grille. Dust is the #1 cause of false alarms in year 2 and beyond.
4. Year 10 (or per the manufacture-date sticker): replace the entire unit. Sealed-battery detectors are not serviceable; the sensor itself degrades.
5. CO detectors: electrochemical CO sensors have a hard 7-year lifespan even in combo units rated for 10. Most modern combos end-of-life the entire device when CO sensor expires, which is correct. Replace, don’t try to extend.

What about smart home integration?

This is where the post-Nest market falls down. The Nest Protect was elegant because Google integrated it natively into Google Home and the alarm-state changes triggered automations directly (turn on hall lights at night, unlock the front door). The First Alert SC5 replicates most of this for Google Home users. Onelink Safe & Sound replicates it for Apple Home. Kidde P4010ACS-W does almost none of it; you get phone alerts and that is the extent.

If automation matters more than budget, pay the premium for the SC5 or Onelink. If you just want a louder alarm with notifications, the Kidde or X-Sense saves you $50 per unit.

For more on building a balanced ecosystem, see our smart home starter kit guide and Apple Home vs Google Home vs Alexa comparison.

The bottom line

The death of the Nest Protect cleared the way for a more honest market. The First Alert SC5 is the new default for Google Home households, the Onelink Safe & Sound is the only credible Apple Home pick, and X-Sense XS01-WT is the answer for renters and budget-conscious homeowners.

Skip anything without a UL 217 certification number printed on the box. Skip “Matter” claims; the spec does not exist for this device class in 2026. And mark your calendar for your detector’s 10-year birthday: replacing it on schedule is the single biggest thing you can do for home fire safety.