6 Best Smoke And CO2 Alarms [Reviewed] in 2021

(Disclosure: I research online to find the best products, and As an Associate, I earn from qualifying purchases.)

Smoke detectors are a must to keep your home safe from fire by detecting flaming and smoldering fires. CO detectors, on the other hand, are required for any home that uses fuel-burning appliances such as water heater, cooktop, grill or a furnace.Best-Smoke-And-CO2-Alarms

Additionally, those living in electric homes need also to install the CO detectors as carbon monoxide can seep into the house from a nearby garage or backup generator. Are you searching for the best smoke and CO2 alarms to buy?

If so then you’re in the right place. What I can tell you is finding the ideal smoke and CO alarms to buy can be tricky. The smoke and CO detectors market is overflowing with different types and models which makes it super hard to pick one to purchase.

But with this best smoke and CO2 alarms review and guide, you will be able to make the process simpler and find a model that will keep your home safe.

Top 6 Best Smoke And CO2 Alarms for 2021

1. Nest Protect Second Generation – Smoke and Carbon Monoxide Alarm

Nest Protect Second Generation Smoke and Carbon Monoxide AlarmMy first best smoke and CO alarm is the Nest Protect Battery Powered Alarm. It’s the second generator which has been redesigned inside out.

One thing that makes it be in this list is the use industrial grade smoke sensor which tests itself automatically, hushed from a smartphone and lasts for more than ten years.

The best part about this best smoke and CO alarm is that it tells by speaking if there is smoke or carbon monoxide while also directing you where the smoke/CO is so that you can proceed with caution. Because it can connect to your smartphone, the Nest Protect sends a message when there is a problem.


  • Long-life AA Energizer Lithium batteries
  • Omnidirectional microphone
  • Electrochemical CO sensor
  • Split-Spectrum Sensor
  • Ambient light sensor
  • Wi-Fi connection


  • Expensive

2. First Alert BRK SC9120LBL – Hardwired AC Smoke and CO Detector

My second model in this best smoke and CO2 alarms review is the First Alert SC9120LBL BRK Detector. It comes as a robust wired smoke and carbon monoxide alarm that uses an ionization smoke sensing chamber and on the other hand, it uses the electrochemical carbon monoxide sensor.

It also comes with a 10-year battery backup which allows it to offer continued monitoring even when there is a power outage. The best part is that it uses intelligent sensing technology which is employed to reduce false alarms and a single mute button silences them if they occur.

Lastly, but not least, the system features a latching alarm indicator that automatically identifies the smoke sensor that initiated the alarm even after the conditions which set off the alarm have subsided.


  • Electrochemical Carbon Monoxide sensing
  • Hardwired and simple to use
  • Intelligent smoke sensing
  • Single test/silence button
  • 10-year limited warranty
  • 10-year lithium battery
  • UL Approved


  • Installation isn’t that easy

3. Kidde KN-COSM-IBA – Hardwired Smoke and CO Detector Alarm

Kidde KN-COSM-IBA Hardwired Smoke and CO Detector AlarmKidde isn’t a new name in this industry, and it’s a brand name that deserves its fame. My next product is a well-performing Kidde KN-COSM-IBA hardwired smoke and CO alarm.

The alarm reliability comes from the use of intelligent sensor technology with the combination of ionization smoke sensor capabilities. With this combination, the sensors can detect smaller and less visible smoke/fire particles.

The CO sensors use the improved electrochemical sensor. It also includes a backup battery which allows it to provide continuous monitoring even when the power goes off.

Additionally, the alarm features indicator lights on its face which goes on when the sensors sense the presence of smoke or carbon monoxide. I wouldn’t forget to mention that the loud 85dB siren produces clear, loud warning upon detection.


  • Ionization Sensor Technology
  • Dangerous level Red LED flash
  • Battery Lockout System
  • Peak Level Memory
  • Smart Interconnect
  • Interconnectable


  • Many instances of false alarm

4. First Alert 2-in-1 Wireless – Z-Wave Smoke & Carbon Monoxide Alarm

First Alert 2-in-1 Wireless Z-Wave Smoke & Carbon Monoxide AlarmThe First Alert 2-in-1-wave is my next smoke and carbon monoxide alarm. It’s a wireless, battery-operated unit that is designed for compatibility with all certified First Alert enabled Z-Wave devices.

It is equipped with an insect-screened photoelectric smoke sensor chamber and an electrochemical CO sensor. The two work in handy to keep you alert when there is a fire or CO hazard in your home. The system also has an 85-decibel horn which provides a precise, loud warning when the unit detects smoke/CO.

Additionally, it comes with a single silence/test button which makes it easy to mute the alarm when there is a false alarm or when the problem is solved.


  • Photoelectric smoke-sensing technology
  • Tamper-resistant battery drawer
  • Include the test/silence button
  • Side-access battery door
  • Easy-to-install


  • Z-Wave hub sold separately
  • Not compatible with Onelink or WINK

5. Kidde I12010SCO Hardwired – Smoke & Carbon Monoxide Detector Alarm

Kidde I12010SCO Hardwired Smoke & Carbon Monoxide Detector AlarmHere is another well-performing Smoke and CO alarm, the Kidde i12010SCO Worry-Free Alarm. It is hardwired smoke and carbon monoxide alarm that features a lithium battery backup.

The battery is used to ensure that it runs continuously without a stop even when there is a power outage. One of the reasons why I featured it in this best smoker and CO alarms review is the fact that it utilizes breakthrough technology to ensure it offers a quick response to real fire smoke as well as protecting you from CO.

The technology also reduces the chances of false alarms dramatically. Another reason is that this alarm system utilizes intelligent sensor technology which combines the electrochemical CO sensor and the ionization smoke sensor and the two work together to ensure that your home is protected from fire and CO as well and from one unit.


  • Sealed-In Lithium Battery Backup
  • Ionization Sensing Technology
  • Interconnection capability
  • Voice Warning System
  • Hush Feature


  • No warranty

6. First Alert Onelink – Smoke and CO Alarm

First Alert Onelink Smoke and CO AlarmMy last product here is a very unique and innovative model that you will love. The First Alert Onelink Safe & Sound alarm is a smoke detector as well as a carbon monoxide detector alarm.

It features a premium home speaker that connects to Alexa. Apart from being a 3-in-1 unit, this alarm brings a hands-free voice-controlled speaker with a great audio experience.

With this system, you will be able to protect your home and your family from fire and carbon monoxide easily. It’s powered by First Alert’s intelligent smoke and CO protection and warns when there is any fire or carbon monoxide danger in your house. Its 85dB alarm is clear and loud enough to ensure that you hear the warning sound.


  • Omni-directional speaker
  • Easy Mobile Controls
  • Interconnectivity
  • Easy To Install
  • Alexa Enabled
  • Voice Alerts


  • Quite expensive

Best Smoke and Co2 Alarms Buyer’s Guide:

Don’t settle on a Smoke and Co Alarm that you aren’t confident with. Here are some factors you need to use to ensure that the choice you make is a perfect one for you.

Battery-operated vs. hardwired detectors

When you’re searching for the best smoke and CO2 alarms, it’s is crucial that you determine what kind of power source you need to use. Smoke and CO alarms are either battery operated or hardwired. The battery-operated alarms run through a cell battery. They sound a tone, usually a chirping to alert you when the battery needs recharging. These type of smoke and CO alarms requires that you test them at least a month and make sure you change the batteries whenever necessary.

On the other hand, hardwired alarms tie directly into the building power supply. In case of a power outage, they run on battery backup. Same to the battery operated ones, you need to test them too at least once in a month to ensure that the cells are still functional. You need to pick a model that will give an easy time. If you’re installing the units in a fully furnished home, then you need the battery powered since they do not need any wiring.

Types of sensors

Smoke and CO alarms use various sensors to detect the toxic gases inside your home. For example, smoke detectors use either photoelectric sensors or Ionization sensors. With photoelectric sensors, they use light reflecting off smoke particles to have the alarm triggered. It happens when the light produced by the detector bulb reflects into the system’s photocell. With the Ionization sensors, the detector sensor detects smoke by ionizing air particles around it. When attached to smoke particles, electricity flow through the ionized smoke particles thus setting the alarm off.

On the other hand, CO detectors and alarms, use either biometric sensors or electrochemical sensors or the semiconductor sensors. The biometric sensor uses synthetic hemoglobin which darkens in the presence of carbon monoxide, which then connects to the light sensor and set the alarm off if CO is detected.

With electrochemical sensors, they use electric current to detect the amount of carbon monoxide in the air. When the carbon monoxide levels are high around the sensors they sensors the alarm off, they are the most accurate sensors in detecting CO. Lastly we got the semiconductor sensors which works use elevated levels of CO to trigger an alert by diminishing the resistance at the semiconductor sensing unit.


Best smoke and CO2 alarms should last for more than five years. You need to pick a smoke and CO alarm that will require less maintenance and still last for years. Do not confuse the battery life with alarm life. However, you will find that the wired smoke and CO alarms come with 10-year battery backup which I would say is quite impressive.


Silence button: Silence button is a feature that works great at muting a smoke and CO alarm when there is a false alarm. It’s a must to have featured as it will keep you from hitting the unit to make it silent.

Alarm horn: How loud is the alarm? Will it be able to provide a clear, loud alarm to alert you? You need to make sure that the smoke and CO alarm you buy has loud alarms to make sure you hear. Get a system with around 85dB warning.

Best Smoke And CO2 Alarms (FAQs)

Q: What produces carbon monoxide (CO) in the home?

A: Carbon monoxide (CO) is found in fumes produced when you burn fuel in small engines, cars or trucks, lanterns, grills, stoves, gas ranges, fireplaces, or furnaces. CO can build up indoors and cause poisoning to the people and animals who breathe it.


I don’t there is anything more I can add on that. I have given you all the necessary info you need to make sure you make the right decision. The review gives you the best models available, and the information is there to make sure you get your right smoke and CO alarm to keep you safe and alert. So, do not skip any point.

Related Buyer’s Guides Review Lists:

About the author

Sharif Miah

I'm Sharif Miah, is a Blogger and currently doing BBA program. At the weekends and vacations, I love to do Grilling & BBQ party alone with family and friends.

Leave a Comment