Best of
The Best Smart Smoke & CO Detectors (2027)
The best smart smoke and CO detectors for 2027, ranked on sensor quality, interconnect behavior, alert paths, and 10-year ownership cost.
The short answer
The Google Nest Protect (2nd Gen) is the best smart smoke and CO detector for 2027. For whole-home battery interconnect, choose X-Sense SC07-W. For Ring or SmartThings homes, choose the First Alert ZCOMBO.
Our top picks at a glance
- Google Nest Protect (2nd Gen)The premium split-spectrum alarm that speaks, self-tests, and lights your path.Best overall
- Kidde Smart Smoke & CO Detector 30CUAR-WKidde hardwired smart combo alarm with voice alerts and app notifications.Best value combo
- X-Sense SC07-W Wireless InterconnectedInterconnected combo alarms that all sound together, with a 10-year sealed battery.Best interconnected battery set
- First Alert Z-Wave Smoke & CO Alarm ZCOMBOThe hub-home combo alarm: Z-Wave alerts through Ring Alarm or SmartThings, no Wi-Fi needed.Best for hub homes
- First Alert Onelink Safe & SoundA hardwired smoke and CO alarm that doubles as an Alexa smart speaker.Best hardwired upgrade
What owners report
Synthesized from recurring themes in long-term owner feedback.
Most praised
- Phone alerts while traveling are the feature owners say justified the entire purchase
- Voice room announcements end the guesswork of which alarm is sounding
- Fewer cooking false alarms after upgrading to photoelectric and split-spectrum models
- App silencing from the hallway beats the broom-handle-on-the-button routine
Common complaints
- Low-battery and end-of-life chirps still choose the middle of the night
- App account migrations and Wi-Fi changes can orphan alarms until re-paired
- Premium per-room pricing makes whole-home coverage a phased project
- End-of-life replacement of sealed units surprises owners at year ten
The picks, ranked
| # | Product | Award | Sensors | Power | Connectivity | Lifespan | Certification |
|---|---|---|---|---|---|---|---|
| 1 | Google Nest Protect (2nd Gen) | Best overall | Split-spectrum smoke, CO, humidity, temperature, occupancy | Battery (6 AA lithium) or hardwired 120V model | Wi-Fi, Thread interconnect between Protects | 10 years, CO sensor rated 10 years | UL 217 and UL 2034 listed |
| 2 | Kidde Smart Smoke & CO Detector 30CUAR-W | Best value combo | Photoelectric smoke, electrochemical CO | Hardwired with 2 AA battery backup (included) | Kidde app enabled, interconnected | - | - |
| 3 | X-Sense SC07-W Wireless Interconnected | Best interconnected battery set | Photoelectric smoke, electrochemical CO | 10-year sealed lithium battery | RF wireless interconnect (868/915MHz by region) | 10 years | UL 217 and UL 2034, EN standards by region |
| 4 | First Alert Z-Wave Smoke & CO Alarm ZCOMBO | Best for hub homes | Photoelectric smoke, electrochemical CO | 2 AA batteries | Z-Wave (hub required) | 7 to 10 year sensor life by model date | UL 217 and UL 2034 listed |
| 5 | First Alert Onelink Safe & Sound | Best hardwired upgrade | Photoelectric smoke, electrochemical CO | 120V hardwired with battery backup | Wi-Fi, Bluetooth; Alexa built in | 10-year alarm life | UL 217 and UL 2034 listed |
| 6 | Kidde Smart Smoke & CO Detector with Ring | Best Ring-connected combo | Smoke and carbon monoxide | Hardwired with AA battery backup | Ring app enabled | - | - |
| 7 | Kidde Smart CO Alarm | Best dedicated CO | Electrochemical carbon monoxide | 120V plug-in with battery backup | Wi-Fi 2.4GHz | 10-year alarm life | UL 2034 listed |
| 8 | X-Sense XS0B-MR121 Smart Smoke Detector with Base Station | Best budget Wi-Fi smoke | Photoelectric smoke only | Battery powered alarms; base station plug-in | Wi-Fi via SBS50 base station, wireless interconnect | - | - |
| 9 | X-Sense SC07 | Best LCD combo value | Photoelectric smoke, electrochemical CO with LCD | 10-year sealed lithium battery | RF interconnect capable; no direct Wi-Fi | 10 years | UL 217 and UL 2034 by regional model |
| 10 | First Alert SMICO100 Hardwired Interconnected | Best code-driven replacement | Photoelectric smoke, electrochemical CO | 120V hardwired, AA battery backup | Wired interconnect (up to 18 devices) | 10-year alarm life | UL 217 8th edition and UL 2034 listed |
Best overall
Google Nest Protect (2nd Gen)
The premium split-spectrum alarm that speaks, self-tests, and lights your path.
Protect is the alarm that behaves like a safety system: split-spectrum sensing that resists cooking false alarms, spoken room-and-threat alerts, app silencing, nightly self-tests, and a pathlight. Per room it costs the most here, and per avoided 3 a.m. nuisance alarm it earns it back.
Strengths
- Split-spectrum photoelectric sensor reduces cooking false alarms
- Voice alerts name the room and threat before the siren
- Silence from the app when you are nearby
- Nightly Promise self-check and a pathlight that glows on motion
Limitations
- Premium price multiplies across a whole home
- 10-year sealed life means full unit replacement at expiry
- Google Home migration left some legacy Nest app users frustrated
| Sensors | Split-spectrum smoke, CO, humidity, temperature, occupancy |
|---|---|
| Power | Battery (6 AA lithium) or hardwired 120V model |
| Connectivity | Wi-Fi, Thread interconnect between Protects |
| Lifespan | 10 years, CO sensor rated 10 years |
| Certification | UL 217 and UL 2034 listed |
Best for: Homes wanting the best app alerts, voice alarms, and nuisance-alarm intelligence.
Skip if: Budget matters; Protect costs several times a basic smart alarm per room.
Best value combo
Kidde Smart Smoke & CO Detector 30CUAR-W
Kidde hardwired smart combo alarm with voice alerts and app notifications.
Kidde pairs credible combo sensing with voice alerts, interconnect, and app notifications at a mid price. For families wanting one modern alarm per floor without Nest pricing, the 30CUAR-W is the balanced buy.
Strengths
- Photoelectric smoke plus electrochemical CO sensing in one unit
- Voice alerts announce the threat in the home
- Kidde app enabled for remote status and notifications
- Interconnects with other compatible Kidde alarms
Limitations
- Hardwired install; not a battery-only retrofit
- Backup batteries are replaceable AA cells, not a sealed 10-year pack
- App features depend on a Kidde account and home Wi-Fi
| Sensors | Photoelectric smoke, electrochemical CO |
|---|---|
| Power | Hardwired with 2 AA battery backup (included) |
| Connectivity | Kidde app enabled, interconnected |
| Dimensions | 5 x 5 x 2 in, 1.3 lb |
| Model | 30CUAR-W |
Best for: Families wanting Kidde alarm credibility plus app alerts in hardwired locations.
Skip if: You have no alarm wiring boxes; this model is hardwired with battery backup.
Best interconnected battery set
X-Sense SC07-W Wireless Interconnected
Interconnected combo alarms that all sound together, with a 10-year sealed battery.
The SC07-W solves the multi-story problem without wiring: when one unit detects, every unit sounds, on a 10-year sealed battery. Add the base station path for phone alerts and it becomes the most scalable battery system here.
Strengths
- Wireless interconnect: one alarm triggers all units
- 10-year sealed lithium battery, zero battery chores
- Photoelectric smoke plus electrochemical CO
- Multi-packs price whole-home coverage reasonably
Limitations
- Remote phone alerts require the optional base station ecosystem
- Brand app ecosystem is younger than Nest or Kidde
- No voice location announcements
| Sensors | Photoelectric smoke, electrochemical CO |
|---|---|
| Power | 10-year sealed lithium battery |
| Connectivity | RF wireless interconnect (868/915MHz by region) |
| Lifespan | 10 years |
| Certification | UL 217 and UL 2034, EN standards by region |
Best for: Multi-story homes needing whole-house sounding without hardwiring.
Skip if: You want phone alerts out of the box; interconnect is RF, app needs the SBS50 base on supported setups.
Best for hub homes
First Alert Z-Wave Smoke & CO Alarm ZCOMBO
The hub-home combo alarm: Z-Wave alerts through Ring Alarm or SmartThings, no Wi-Fi needed.
ZCOMBO puts smoke and CO inside Ring Alarm and SmartThings, where automations can flash lights, unlock doors for responders, and alert through the security system you already monitor. It is invisible infrastructure, exactly what hub homes want from an alarm.
Strengths
- Integrates alarms into Ring Alarm and SmartThings automations
- Battery powered, mounts anywhere without wiring
- Photoelectric smoke plus electrochemical CO in one unit
- Hub alerts work even though the alarm itself is not Wi-Fi
Limitations
- Requires a compatible Z-Wave hub for any smart feature
- No voice or room-naming alerts
- Not a primary Ring Alarm monitored sensor in all configurations, check your plan
| Sensors | Photoelectric smoke, electrochemical CO |
|---|---|
| Power | 2 AA batteries |
| Connectivity | Z-Wave (hub required) |
| Lifespan | 7 to 10 year sensor life by model date |
| Certification | UL 217 and UL 2034 listed |
Best for: Ring Alarm and SmartThings homes wanting alarms inside the security system.
Skip if: You have no Z-Wave hub; this alarm has no standalone app.
Best hardwired upgrade
First Alert Onelink Safe & Sound
A hardwired smoke and CO alarm that doubles as an Alexa smart speaker.
Safe and Sound turns a required ceiling box into an Alexa speaker, nightlight, and premium combo alarm in one install. For hardwired homes renovating room by room, nothing else multitasks like it, though buyers should confirm current line support before a whole-home order.
Strengths
- Built-in Alexa speaker for music and voice in alarm locations
- Photoelectric smoke plus electrochemical CO sensing
- Hardwired interconnect with other Onelink and many BRK alarms
- Adaptive nightlight and strong First Alert app alerts
Limitations
- Hardwired only; no battery-only version
- Discontinued-line risk: verify current stock and support before whole-home buys
- Speaker features raise the price well above alarm-only rivals
| Sensors | Photoelectric smoke, electrochemical CO |
|---|---|
| Power | 120V hardwired with battery backup |
| Connectivity | Wi-Fi, Bluetooth; Alexa built in |
| Lifespan | 10-year alarm life |
| Certification | UL 217 and UL 2034 listed |
Best for: Hardwired homes wanting Alexa in the ceiling plus premium alarm features.
Skip if: You lack hardwired alarm boxes; Safe and Sound is AC-powered only.
Best Ring-connected combo
Kidde Smart Smoke & CO Detector with Ring
The Ring-connected Kidde combo: hardwired smoke and CO with Ring app alerts.
The Kidde with Ring puts smoke and CO alerts inside the Ring app Ring households already live in, on hardwired power with battery backup. It is the combo alarm for homes whose security already runs through Ring.
Strengths
- Smoke plus CO sensing from a traditional alarm brand
- Ring app enabled alerts alongside Ring cameras and doorbells
- Hardwired reliability with AA battery backup
- One app for security and life-safety alerts
Limitations
- Premium pricing for the Ring-connected model
- Hardwired install only; no battery-only version
- Smart features center on the Ring app ecosystem
| Sensors | Smoke and carbon monoxide |
|---|---|
| Power | Hardwired with AA battery backup |
| Connectivity | Ring app enabled |
| Model | RGCUAR-RW |
| Brand | Kidde |
Best for: Ring households wanting combo alarms that report inside the Ring app.
Skip if: You have no hardwired alarm boxes, or no interest in the Ring ecosystem.
Best dedicated CO
Kidde Smart CO Alarm
Plug-in smart CO detection with battery backup and app alerts for furnace rooms.
CO risk concentrates near furnaces, garages, and generators, and a dedicated plug-in smart CO alarm with app alerts covers it better than hoping a hallway combo is close enough. Peak-level memory also helps a technician diagnose intermittent problems.
Strengths
- Dedicated electrochemical CO sensing with digital display lineage
- Plug-in power with battery backup rides out outages
- Wi-Fi app alerts for CO events away from home
- Peak-level memory helps diagnose intermittent furnace issues
Limitations
- CO only; pair with smoke alarms for full coverage
- Occupies an outlet near the floor or appliance
- Smart features depend on Kidde app availability in your region
| Sensors | Electrochemical carbon monoxide |
|---|---|
| Power | 120V plug-in with battery backup |
| Connectivity | Wi-Fi 2.4GHz |
| Lifespan | 10-year alarm life |
| Certification | UL 2034 listed |
Best for: Homes adding connected CO coverage near fuel-burning appliances.
Skip if: You need smoke sensing too; this is a CO-only device by design.
Best budget Wi-Fi smoke
X-Sense XS0B-MR121 Smart Smoke Detector with Base Station
A Wi-Fi smoke alarm kit with voice location alerts and an SBS50 base station.
For a single room or rental, the XS0B-MR kit gives real phone smoke alerts and voice location announcements at the lowest connected price here. It is smoke only, a limit that is fair at the price and fixable by pairing a CO alarm.
Strengths
- Wi-Fi phone alerts through the included SBS50 base station
- Voice alerts name the location across 17 preset locations
- Wireless interconnect: when one alarms, the set sounds together
- Test and silence from the X-Sense app
Limitations
- Smoke only; no CO sensor
- Phone alerts route through the base station, not direct Wi-Fi
- Base station needs its own outlet and 2.4GHz Wi-Fi
| Sensors | Photoelectric smoke only |
|---|---|
| Power | Battery powered alarms; base station plug-in |
| Connectivity | Wi-Fi via SBS50 base station, wireless interconnect |
| Alerts | Voice location alerts, app notifications |
| Model | XS0B-MR (kit XS0B-MR121) |
Best for: Apartments and homes needing phone smoke alerts cheaply; smoke only, pair with a CO alarm.
Skip if: You need CO sensing in the same unit; the XS0B-MR is smoke only.
Best LCD combo value
X-Sense SC07
The standalone SC07 combo: LCD CO display and 10-year battery, base for interconnected sets.
The SC07 LCD showing live CO in PPM is genuinely useful information most alarms hide, and the 10-year sealed design plus interconnect capability make it a smart foundation unit for a growing X-Sense set.
Strengths
- LCD shows real-time CO concentration in PPM
- 10-year sealed battery and sensor life
- Can wirelessly link with SC07-W units in mixed sets
- Lower price than the pure interconnect model
Limitations
- Standalone unit has no direct phone app alerts
- No voice announcements
- App ecosystem requires stepping up to base-station models
| Sensors | Photoelectric smoke, electrochemical CO with LCD |
|---|---|
| Power | 10-year sealed lithium battery |
| Connectivity | RF interconnect capable; no direct Wi-Fi |
| Lifespan | 10 years |
| Certification | UL 217 and UL 2034 by regional model |
Best for: Budget combo coverage and the starting unit for an X-Sense interconnected system.
Skip if: You want phone alerts from this unit alone; smart alerts need interconnected base or Wi-Fi siblings.
Best code-driven replacement
First Alert SMICO100 Hardwired Interconnected
Hardwired interconnected combo alarm with battery backup for code-driven replacements.
When an inspector, insurer, or local code demands hardwired interconnected alarms, the SMICO100 is the straightforward compliant replacement with modern UL 217 8th-edition sensing and adapter-friendly wiring. Its smart feature is the oldest one: every alarm sounds, everywhere.
Strengths
- Hardwired interconnect sounds every alarm for one event
- Photoelectric smoke plus CO with battery backup
- Adapter plugs ease replacement of common legacy brands
- Meets modern code expectations for interconnected coverage
Limitations
- No direct app or voice-assistant alerts
- Hardwired install may need an electrician
- Smart-home value is indirect, via whole-home audibility
| Sensors | Photoelectric smoke, electrochemical CO |
|---|---|
| Power | 120V hardwired, AA battery backup |
| Connectivity | Wired interconnect (up to 18 devices) |
| Lifespan | 10-year alarm life |
| Certification | UL 217 8th edition and UL 2034 listed |
Best for: Replacing hardwired alarms where interconnect sounding is required by code or insurer.
Skip if: You want phone app alerts; this is an interconnected alarm, smart through whole-home sounding, not Wi-Fi.
How we chose
Certified sensing first
Every pick carries mainstream UL or EN certification with photoelectric smoke sensing favored for smoldering fires and fewer nuisance alarms. Smart features never outranked sensor credibility.
The alert must reach you
We traced each alarm path to a phone: Nest and Kidde by Wi-Fi, ZCOMBO by hub, X-Sense sets by interconnect and optional base. Picks whose limits differ are labeled in plain language.
Whole-home sounding
A kitchen detection must wake a basement sleeper. Interconnect, wired, RF, or Thread, counted as a core safety feature, not an accessory.
Ten-year ownership
Sealed 10-year batteries, sensor expiry, and replacement-unit cost decide real price. We favored alarms whose decade of ownership involves the fewest batteries and surprises.
Questions, answered
How many smoke and CO alarms does a home need?
Follow NFPA guidance and local code: smoke alarms inside every bedroom, outside sleeping areas, and on every level; CO alarms outside sleeping areas and on levels with fuel-burning appliances. Interconnect them so all sound together.
Photoelectric or ionization smoke sensing?
Photoelectric responds faster to smoldering fires and false-alarms less near kitchens, which is why most picks here use it. Dual-sensor and split-spectrum designs broaden coverage further.
Do smart alarms work during an internet outage?
The alarm siren always works locally; interconnect generally works too. Phone alerts are what an outage suspends. Hardwired and battery alarms protect the home regardless of Wi-Fi.
When must I replace a smart alarm?
At its printed expiry, typically 10 years from manufacture for smoke and CO sensors. Smart features do not extend sensor life; the app on Nest and Kidde models will warn you as expiry approaches.