First Alert SC5 Smart Smoke & CO Alarm
By Ethan Halfhide · Updated
First Alert lists the SC5 Battery and SC5 Hardwire Smart Smoke and Carbon Monoxide Alarms at $129.99 each on firstalert.com as of October 2026; on October 21, 2026 the SC5 Battery page said it was backordered and would ship when back in stock, while the SC5 Hardwire could be added to the cart. First Alert describes the SC5 as compatible with and a replacement for Google's Nest Protect, and Google's own help center names the First Alert Smart Smoke & CO Alarm as the compatible replacement for an expiring Nest Protect when used with the Google Home app. Both versions pair a photoelectric smoke sensor with an electrochemical CO sensor and First Alert's Precision Detection technology, which First Alert says meets updated industry standards to give early warning and reduce cooking nuisance alarms. They sound an 85 dB alarm with voice alerts and a Heads-Up warning that tells you the type and location of danger, send mobile alerts through the Resideo Connect app, and give in-app and audible notices when the alarm needs replacing. They interconnect with compatible First Alert alarms and with Google Nest Protect, so when one sounds they all sound. The battery model (SMCO600NV) runs on six replaceable 3V CR123A lithium batteries and links wirelessly. The hardwire model (SMCO600NV-AC) supports hardwired interconnect, has a lithium battery backup that is not replaceable, and includes a Quick Connect plug for installation with no need to rewire. Both conform to UL 217 10th Edition, measure 5.75 x 5.75 x 1.6 inches and carry a 10-year limited warranty.
Wi-Fi smoke and CO alarm that interconnects with and replaces Nest Protect
First Alert SC5 Smart Smoke & CO AlarmProduct images: First Alert SC5 Smart Smoke & CO Alarm
Specs and price last verified October 21, 2026
About
The First Alert SC5 is a smart smoke and carbon monoxide alarm sold in a battery model (SMCO600NV, six replaceable CR123A lithium batteries) and a hardwire model (SMCO600NV-AC, with a lithium battery backup and a Quick Connect plug). It uses photoelectric and electrochemical sensors with First Alert's Precision Detection, sounds voice alerts with a Heads-Up warning that names the type and location of danger, sends phone alerts through the Resideo Connect app, and interconnects with compatible First Alert alarms and Google Nest Protect. Google names it as the compatible replacement for Nest Protect in the Google Home app.
Setup and compatibility notes
- Pick a version: the SC5 Battery (SMCO600NV) uses six 3V CR123A lithium batteries that you can replace. The SC5 Hardwire (SMCO600NV-AC) runs on household wiring with a lithium battery backup and ships with a Quick Connect plug, which First Alert says allows installation with no need to rewire.
- App: set the alarm up in the Resideo Connect app, which First Alert links on the App Store and Google Play. The app checks alarm status, tests the alarm and sends mobile alerts for smoke and CO.
- Adding to Nest Protect: First Alert says Nest Protect compatibility requires the Google Home app and a Google Account. Google's steps: migrate any Nest account to a Google Account, update the Google Home app and First Alert app, set up the alarm in the First Alert app (QR code, location, names, Wi-Fi) and tap Link if you have a Nest Protect, then add it in Google Home. Keep your Nest Protect within range.
- Mounting: Google recommends ceiling mounting; on a wall, Google says to place it within 12 inches of the ceiling.
- Maintenance: test from the app or the single test/silence button, and First Alert says to clean the alarm monthly by dusting or gently vacuuming.
- Availability: on October 21, 2026 the SC5 Battery showed as backordered on firstalert.com; the SC5 Hardwire could be added to the cart.
Pros
- +Works with and replaces Google Nest Protect
- +Interconnects so when one alarm sounds, all compatible alarms sound
- +Voice alerts with Heads-Up warning name the danger and location
- +Phone alerts, status checks and alarm tests in the Resideo Connect app
- +Battery and hardwire versions at the same price
- +10-year limited warranty
Cons
- −SC5 Battery listed as backordered on firstalert.com on October 21, 2026
- −Nest Protect compatibility needs the Google Home app and a Google Account
- −Battery model uses six CR123A lithium batteries
- −Hardwire model's backup battery is not replaceable
- −No Matter, Alexa or Apple Home support listed by First Alert
How it compares
| Device | Price | Ecosystems | Matter | Hub required | Local control |
|---|---|---|---|---|---|
| First Alert SC5 Smart Smoke & CO Alarm | $129.99 | Google Home | No | No | Not published |
| Kidde Smart Smoke + CO Alarm (30CUAR-W) | Not listed | Alexa, Google Home | No | No | Not published |
| Google Nest Protect | Not listed | Google Home | No | No | Not published |
| SimpliSafe Smoke Detector | $35 | Alexa, Google Home | No | Yes | No |
FAQ
- How much does the First Alert SC5 cost?
- First Alert lists both the SC5 Battery and SC5 Hardwire models at $129.99 on firstalert.com as of October 2026. On October 21, 2026 the battery model was backordered and the hardwire model could be added to the cart.
- Does the SC5 work with Google Nest Protect?
- Yes. First Alert says it is compatible with and replaces Nest Protect, which requires the Google Home app and a Google Account, and Google says it can relay smoke or CO events to and from Nest Protect alarms in range.
- What is the difference between the battery and hardwire SC5?
- The battery model uses six replaceable CR123A lithium batteries and wireless interconnect. The hardwire model runs on household wiring with a non-replaceable lithium backup battery, supports hardwired interconnect and includes a Quick Connect plug.
- Which app does the SC5 use?
- First Alert's product pages name the Resideo Connect app for checking alarm status, running alarm tests and getting mobile alerts. Google's help page also uses the Google Home app to add it to a Nest home.
- What warranty does the SC5 have?
- First Alert lists a 10-year limited warranty for both versions.
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Google Nest Protect
Discontinued by Google in the US store; still supported, with First Alert SC5 named as the replacement
About the author
Ethan Halfhide: Ethan Halfhide is a smart home enthusiast and AI technologist who follows the connected home market closely, from smart locks and security cameras to robot vacuums, lighting, sensors and hubs. He curates HomeGearLab's device directory, comparing products on published specs, compatibility, setup requirements and price so readers can pick gear that fits their home and works together.