Best Smart Smoke and CO Detectors (2026)
A smart smoke and carbon monoxide (CO) alarm sounds like any other alarm, but also sends an alert to your phone when you're away. With Google no longer making Nest Protect, this guide covers the replacement options, what to check before you buy, and four smoke and CO alarms from First Alert and Kidde.
Affiliate disclosure: As an Amazon Associate, Everyday Tech Guide earns from qualifying purchases. This page contains labeled affiliate links; we may earn a commission if you purchase through them, at no additional cost to you. Our picks are not paid placements.
Quick picks
- Best Nest Protect replacement: First Alert SC5 Smart Smoke & CO Alarm
- Best for Alexa and Google Home with Kidde wiring: Kidde Smart Smoke + CO Alarm 30CUAR-W
- Best for Ring homes: Kidde Smart Smoke + CO Alarm with Ring, hardwired (RGCUAR-RW)
- Best with no wiring: Kidde Smart Smoke + CO Alarm with Ring, AA battery (RGCUDR-RW)
Safety first: smart features are an extra layer
Phone alerts, voice warnings and app tests are useful, but they do not replace the smoke and CO alarms your home is required to have. If your home has hardwired, interconnected alarms, keep them working and replace them with compatible models so that when one sounds, they all sound. Follow your local building code and your fire department's guidance on placement, power and interconnection. Notifications depend on Wi-Fi, internet service and your phone, so never count on an app alert alone. Test alarms regularly, and replace them by the date the maker gives.
Replacing a hardwired alarm means working with 120V wiring. Turn off power at the breaker first, and use a licensed electrician if you are unsure or if new wiring is needed.
What happened to Nest Protect?
Google announced in March 2025 that it is no longer making Nest Protect. Google's support pages say Nest Protect is no longer available for sale but is still supported, and that the 2nd gen model must be replaced 10 years from its date of manufacture. Google partnered with First Alert on the SC5 Smart Smoke and CO Alarm as the compatible replacement: First Alert says it works with existing Nest Protect alarms in the Google Home app and is designed to fit the Nest Protect mounting plate.
How we chose
Each pick is a combination smoke and CO alarm with photoelectric smoke sensing, sold on Amazon in the US at the time of writing. Certifications, interconnect options and app features come from the makers' product pages, data sheets, manuals and linked certification documents. We have not tested these alarms ourselves. We favored alarms that interconnect with other alarms, keep sounding locally without Wi-Fi, and give phone alerts without a required subscription.
Check the listing: UL 217 and UL 2034
UL 217 is the US standard for smoke alarms and UL 2034 covers residential CO alarms. A testing lab such as UL or Intertek (ETL) certifies a product to these standards. Here is what the makers' documents say for each pick:
- First Alert SC5: First Alert's product pages list conformance to UL 217 10th Edition; the SC5 battery model's installation guide says it conforms to UL 217 and UL 2034.
- Kidde 30CUAR-W and RGCUAR-RW: Kidde links an Intertek (ETL) certification document on each product page that covers both models under UL 217 (10th Edition) and UL 2034 (5th Edition).
- Kidde RGCUDR-RW: Kidde's product data sheet says the unit meets UL 217 and UL 2034 requirements at the date of manufacture.
Before you install, check the label on the alarm itself and confirm it meets what your local code requires.
Comparison at a glance
| Product | Power | App and platforms | Interconnect |
|---|---|---|---|
| First Alert SC5 | Hardwired with battery backup, or battery-only version | First Alert app; Google Home app | Wireless with SC5 and Nest Protect; hardwired version also wires to compatible First Alert and BRK alarms |
| Kidde 30CUAR-W | Hardwired, 2 AA backup | Kidde app; Alexa and Google Home | Hardwired with up to 24 compatible Kidde devices |
| Kidde RGCUAR-RW (Ring) | Hardwired, 2 AA backup | Ring app; no other Ring devices required | Hardwired with up to 24 compatible Kidde devices |
| Kidde RGCUDR-RW (Ring) | 2 AA batteries | Ring app; no other Ring devices required | Wire-free with compatible Kidde alarms |
Best Nest Protect replacement: First Alert SC5 Smart Smoke & CO Alarm
The SC5 is the alarm Google partnered on to replace Nest Protect. It uses photoelectric smoke and electrochemical CO sensors, gives voice alerts with the type and location of the danger, and sends phone alerts through the First Alert app. It also works in the Google Home app, where it can interconnect with existing Nest Protect alarms.
- Power: the hardwired SMCO600NV-AC has a non-replaceable lithium backup battery and a quick-connect plug; the battery-only SMCO600NV uses six replaceable CR123A batteries.
- Interconnect: wireless over 2.4 GHz between SC5 and Nest Protect alarms through the apps; the hardwired version also has wired interconnect with compatible First Alert and BRK alarms.
- Consider: First Alert's own store showed both versions as backordered when we checked, and the Amazon listing may come from third-party sellers; check the seller and the manufacture date on the alarm.
View the First Alert SC5 Hardwire Smart Smoke & CO Alarm (SMCO600NV-AC) on Amazon (affiliate link) →
View the First Alert SC5 Battery Smart Smoke & CO Alarm (SMCO600NV) on Amazon (affiliate link) →
We have not independently tested this product. Availability, specifications and the maker's subscription terms can change; confirm the details on the product listing and the manufacturer's site.
Best for Alexa and Google Home with Kidde wiring: Kidde 30CUAR-W
Kidde's hardwired smart combination alarm connects to 2.4 GHz Wi-Fi and sends smoke, CO and low-battery alerts through the Kidde app. Kidde says adding one smart alarm to an existing Kidde hardwired interconnect gives you phone alerts when any connected alarm sounds, and its data sheet lists compatibility with Alexa and Google Home.
- Power: 120V AC with two AA backup batteries; Kidde says AC power is required for Wi-Fi and full operation.
- Interconnect: hardwired, with up to 24 compatible Kidde devices; Kidde says it is not designed to interconnect with other brands unless specified.
- Consider: you can hush a false alarm from the app, but Kidde notes it may require your phone to be nearby or on the same Wi-Fi.
View the Kidde Smart Smoke + CO Alarm 30CUAR-W (hardwired) on Amazon (affiliate link) →
We have not independently tested this product. Availability, specifications and the maker's subscription terms can change; confirm the details on the product listing and the manufacturer's site.
Best for Ring homes: Kidde Smart Smoke + CO Alarm with Ring (RGCUAR-RW)
This hardwired Kidde alarm uses the Ring app instead of the Kidde app, so smoke and CO alerts show up alongside a Ring doorbell or cameras. Kidde says no other Ring devices are required. An optional Ring subscription adds 24/7 smoke and CO monitoring, where agents can request emergency help; phone alerts do not need a subscription.
- Power: 120V AC with two AA backup batteries.
- Interconnect: hardwired, with up to 24 compatible Kidde devices.
- Consider: professional monitoring is a paid add-on and is limited to the US.
View the Kidde Smart Smoke + CO Alarm with Ring (RGCUAR-RW) on Amazon (affiliate link) →
We have not independently tested this product. Availability, specifications and the maker's subscription terms can change; confirm the details on the product listing and the manufacturer's site.
Best with no wiring: Kidde Smart Smoke + CO Alarm with Ring (RGCUDR-RW)
If you don't have alarm wiring where you need one, this battery-powered version sends Ring app alerts and interconnects wirelessly with compatible Kidde alarms, so when one sounds, they all do. Kidde also lists low-level CO alerts in the Ring app.
- Power: two AA batteries, which Kidde says need replacing about once a year in normal use.
- Interconnect: wire-free, with compatible Kidde alarms.
- Consider: where your code requires hardwired, interconnected alarms, add this alongside them, not instead of them.
View the Kidde Smart Smoke + CO Alarm with Ring, AA battery (RGCUDR-RW) on Amazon (affiliate link) →
We have not independently tested this product. Availability, specifications and the maker's subscription terms can change; confirm the details on the product listing and the manufacturer's site.
Building out the rest of your smart home? See our smart thermostat picks, Matter smart switches and dimmers and the smart doorbell compatibility guide.
For water leak, motion and temperature alerts, see our Matter and Thread sensor picks.
Frequently asked questions
Is Google Nest Protect discontinued?
Yes. Google announced in March 2025 that it is no longer making Nest Protect, and its support pages now say Nest Protect is no longer available for sale but is still supported. Google recommends the First Alert SC5 Smart Smoke and CO Alarm as the compatible replacement for the 2nd gen Nest Protect in the Google Home app. Existing units keep working until they reach their replacement date, 10 years from the date of manufacture.
Do smart smoke alarms replace code-required interconnected alarms?
No. Phone alerts are an extra layer, not a substitute for the alarms your building or local code requires. If your home has hardwired, interconnected smoke alarms, keep that system working and replace like with like. Follow your local building code and your fire department's guidance on where alarms go and how they must be powered and interconnected.
Can I mix smart alarms from different brands?
Usually not on the same interconnect. Kidde says its alarms are not designed to be interconnected with other manufacturers' products unless otherwise specified, and First Alert lists the specific First Alert, BRK and Nest Protect models the SC5 works with. Check the compatibility list before adding a smart alarm to an existing hardwired system.
Where should smoke and CO alarms go?
The NFPA recommends smoke alarms inside each bedroom, outside each sleeping area and on every level of the home, including the basement, and CO alarms outside each sleeping area and on every level. Your local code may require more. Follow the placement section of the alarm's manual, and ask your local fire department if you are unsure.
Do these alarms work with Matter?
None of the picks on this page use Matter. The First Alert SC5 works with the Google Home app, the Kidde app alarm lists Alexa and Google Home compatibility, and the Kidde alarms built for Ring use the Ring app. Treat any smart-home integration as a convenience on top of the alarm's own siren and interconnect.
Should I hire an electrician to install a hardwired smoke alarm?
If you are replacing a hardwired alarm and you are not comfortable with 120V wiring, yes. Turn off power at the breaker first. Replacing an existing alarm with a compatible quick-connect plug can be simpler, but adding new hardwired alarms or interconnect wiring is a job for a licensed electrician and may need a permit.