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A 2nd-generation Google Nest Protect has a 10-year replacement limit measured from its manufacture date—not the date you bought it. Check the alarm’s individual “Replace by” date in the app or on the device. Replacing its batteries does not extend that date.
How long does a Nest Protect last?
Google says 2nd-generation Nest Protect alarms must be replaced 10 years after manufacture. The limit applies to both battery-powered and wired models. Google attributes expiration to the limited lifespan of the carbon monoxide sensor and says to replace the unit when it expires to maintain smoke and carbon monoxide protection. Google’s expiration guidance states the requirement; it is a manufacturer replacement rule, not a published average of how long alarms actually operate or a failure-rate statistic.
The reviewed Google guidance establishes this interval for 2nd-generation Protect only. It does not establish the same interval for 1st-generation models, so check the specific device’s documentation rather than applying the 10-year figure to every generation.
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How to find your alarm’s replacement date
Use the “Replace by” date shown for your device, rather than calculating from its purchase date. Google lists these ways to find it:
#1 Best Overall
- Double the Detection: Alerts you to both smoke and carbon monoxide (CO)
- Real-Time Ring App Notifications: Home or away, get smoke, CO or low battery warnings (no subscription required)
- Over 25% faster smoke detection (based on internal testing vs a leading competitor)
- Optional Ring subscription (sold separately) with 24/7 smoke and CO monitoring for $5/month
- No Wiring Needed: Operates on 2-AA alkaline batteries (included) for simple use throughout your home
- Nest app: Settings > Technical info.
- Google Home app: Settings > Device information > Technical information.
- On the alarm: Read the date printed on the back of the Protect.
Google says expiration reminders in the app and by email require the Protect to be connected to Wi-Fi and set up in the Nest or Google Home app. Its guidance describes reminders starting three months before expiration, including app history indicators, email reminders, and on-device messages. The alarm still chirps after expiration even if it is not connected to an app. A yellow ring or message may mean expiration is approaching; confirm the date in the app or on the device. Google’s replacement-date guidance explains the lookup and reminder details.
Expiration, batteries, and sensor alerts are different
Battery warnings do not reset the expiration date
A low-battery warning means the batteries need attention; it does not change the manufacture-based “Replace by” date. Google specifies Energizer Ultimate Lithium AA (L91) batteries: six for battery-powered Protect and three backup cells for wired Protect. Google warns against rechargeable and alkaline batteries and against mixing battery types or old and new cells. Its battery instructions also say battery-powered Protect warns when roughly a year of battery life remains and escalates alerts as charge falls. For wired units, Google says backup batteries should last the life of the Protect when it has a consistent power source; actual backup use and low-battery alerts still matter.
Rank #2
- Double the Detection: Alerts you to both smoke and carbon monoxide (CO)
- Real-Time Ring App Notifications: Home or away, get smoke, CO or low battery warnings (no subscription required)
- Over 25% faster smoke detection (based on internal testing vs a leading competitor)
- Optional Ring subscription (sold separately) with 24/7 smoke and CO monitoring for $5/month
- Whole Home Smart Connectivity: Get mobile alerts for every hardwired alarm in your home by adding just one Kidde smart detector; check the user guide for more information
Chirp patterns can help distinguish the alerts
Google says critically low batteries produce one chirp every 60 seconds, while an expired Protect gives a double chirp once a minute. An expired alarm does not protect against smoke or carbon monoxide, so do not treat its chirping as a routine battery reminder. See Google’s lights-and-sounds guide for the alert details.
A sensor-failure alert may need cleaning—or replacement
Fire, flooding, solvents, aerosols, vehicle exhaust, and open flames can damage Protect sensors. If a smoke-chamber sensor alert occurs without a major incident, Google advises cleaning the smoke chamber; replace the Protect if the alert continues after cleaning. Google’s expiration and sensor guidance describes this distinction.
Rank #3
- Real-Time Ring App Notifications: Home or away, get smoke or low battery warnings (no subscription required)
- Over 25% faster smoke detection (based on internal testing vs a leading competitor)
- Optional Ring subscription (sold separately) with 24/7 smoke monitoring for $5/month
- No Wiring Needed: Operates on 2-AA alkaline batteries (included) for simple use throughout your home
- Whole Home Smart Connectivity: Get mobile alerts for every Kidde alarm in your home through wire-free interconnectivity — when one alarm sounds, they all do. (Check the user guide for more information)
Replacing an expired Nest Protect
Google identifies the First Alert Smart Smoke & Carbon Monoxide Alarm as a compatible replacement for 2nd-generation Nest Protect when used with the Google Home app. That does not establish compatibility for every First Alert model, wiring arrangement, jurisdiction, or installation. Check the replacement alarm’s current instructions and local fire-safety requirements; Google notes that regional rules vary. Its regional-use information includes guidance for California and New York State.
Have the replacement ready before removing an expired Protect to avoid a gap in protection. If replacing a wired unit, Google instructs users to switch off power at the breaker before touching wiring. Follow the new alarm’s installation instructions and applicable local requirements. Google’s expiration guidance covers replacement and installation cautions.
Quick Recap
Best Value
- 2-in-1 Protection: The smoke and carbon monoxide detector is equipped with both photoelectric smoke sensor and electrochemical CO sensor that both detect smoke and dangerous CO levels
- ETL Listed: The smoke and carbon monoxide alarm meets the UL 217 & UL 2034 safety standards for your peace of mind and absolute confidence in our product
- Simple Installation: Requires no rewiring; easy to mount this fire and CO alarm on any wall or ceiling with the included mounting bracket, screws and anchor plugs
- Combination Alarm with CO Readings: the large LCD display clearly indicates real-time carbon monoxide (CO) levels in the surrounding air, as well as its battery level and working status
Rank #4
- Real-Time Ring App Notifications: Home or away, get smoke or low battery warnings (no subscription required)
- Over 25% faster smoke detection (based on internal testing vs a leading competitor)
- Optional Ring subscription (sold separately) with 24/7 smoke monitoring for $5/month
- Whole Home Smart Connectivity: Get mobile alerts for every hardwired alarm in your home by adding just one Kidde smart detector; check the user guide for more information
- Reduced Nuisance Alarms: Enhanced sensing technology reduces false alarms often caused by cooking when compared to prior Kidde generations of smoke alarms
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