The 8 Best Smoke Detectors of 2021

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The Spruce / Chloe Jeong

Our Top Picks
Easy to install, this battery-powered unit notifies you if it detects smoke, fire, carbon monoxide, or a low battery.
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This affordable unit comes with lithium batteries that will last for 10 years, and uses an ionization sensor to detect smoke particles.
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Hardwired, it uses a photoelectric sensor to detect smoke and a carbon monoxide sensor to detect the deadly gas in your home.
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This unit is hardwired and comes with lithium batteries as a backup power source that will last for 10 years.
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It only requires two AA batteries which can be easily inserted into the pop open panel on the front of the unit.
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With its smart features, you can receive real-time updates through an app on your phone as well as silence false alarms.
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With both photoelectric and ionization sensors, you will be alerted to fast-burning as well as smoldering fires.
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These combination smoke and carbon monoxide detectors come in a pack of three or six and have battery back ups.
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Fire and smoke can be some of the most dangerous emergencies in your home. Detectors and alert systems often test for the presence of smoke, since this is the first sign of trouble and often more deadly than the fire itself.

Smoke detectors use two kinds of sensors: photoelectric and ionization. Photoelectric smoke alarms are best at detecting smoldering fires and may cause fewer false alarms, while ionization smoke alarms are better at detecting sudden, fast-burning fires.  For the ultimate safety, choose a smoke detector with both types of sensors.

Aside from sensor type, the other main consideration is whether or not you need hard-wired detectors. Hard-wired smoke detectors may require an expert for installation, but the major pro is that they only rely on batteries as a backup power source. Battery-operated alarms aren’t hard-wired, making them easier to install and use. The downside, of course, is that they will start chirping when the battery is low. Both hardwired and battery-operated units will alert you when they are near the end of their lifespan, typically after five to 10 years of use.

To make your decision easier, we researched dozens of smoke detectors and evaluated them on the basis of power, lifespan, sensor type, and integration into your whole-home system (if applicable). Each of the detectors chosen in this article was determined to be the best of these factors.

Read on for our top picks.

Best Overall: Kidde Battery-Operated Combination Smoke/Carbon Monoxide Alarm with Voice Warning

Kidde Smoke & Carbon Monoxide Detector

Power Source: Battery operated | Sensor Type: Ionization (smoke) and carbon monoxide | Pack Size: Single

What We Like
  • Voice alerts

  • Easy install

  • Works with other Kidde wall-mount bases

What We Don't Like
  • Batteries need to be changed

There are a lot of great smoke detectors on the market, but this combo unit from Kidde sets the bar for ease of install, superior detection, and multi-type alerts. One of the best features is the voice alerts, which notifies you if it detects fire or smoke, carbon monoxide, low battery, or the hush feature is active. 

Installation is a breeze with the included base. If you have other Kidde products in your home, you can likely use the base you already have since they are compatible. This is a battery-operated unit, so you will need to periodically change the batteries. Fortunately, you can do this without removing the detector from the wall-mounted base.

What Testers Say

"The battery compartment will only shut if the batteries have been installed properly. We like this extra safeguard as it ensures our alarm is always functioning correctly."—Katie Begley, Product Tester

Best Budget: Kidde 10 Year Worry-Free Smoke Detector with Lithium Battery

10 Year Worry-Free Smoke Detector, Lithium Battery Powered

Power Source: Battery operated or hardwired | Sensor Type: Ionization | Pack Size: Single or multi-pack (up to 6)

What We Like
  • 10 year lithium battery

  • Budget-friendly price

  • Multi-pack available

What We Don't Like
  • Only ionization sensor

Don’t let the budget-friendly price fool you. The Kidde 10 Year Smoke Detector has some great features that homeowners will love. It is battery operated, which makes installation easier. But the lithium batteries come installed in the unit and will last for 10 years without ever needing to be changed or chirping in the middle of the night.

This smoke detector uses an ionization sensor to detect smoke particles in the air. It is available in single or multi-packs and does have a slightly pricier hardwired version that uses the lithium battery as a back-up.

Best Smoke and Carbon Monoxide Detector: Kidde FireX Hardwire Smoke and Carbon Monoxide Combination Detector 2 Pack

Kidde FireX Hardwire Smoke and Carbon Monoxide Combination Detector, 2-pack

Power Source: Hardwired | Sensor Type: Photoelectric and carbon monoxide | Pack Size: Two-pack

What We Like
  • Smoke and carbon monoxide detection

  • Units work together

  • Voice alerts

What We Don't Like
  • Professional installation needed

The Firex alarm from Kidde includes a smoke detector and carbon monoxide detector that will alert all hardwired alarms within the system to the threat. It uses a photoelectric sensor to detect smoke and a carbon monoxide sensor to detect the deadly gas in your home. The voice alert tells you which danger is present and the 85 db alarm makes sure that you hear the horn.

Because it is hardwired, these detectors do require professional installation. You can set this up through Home Depot when you purchase the units or look for someone in your local area. After taking care of installation, the interoperability of the units makes sure that you always know of danger no matter where you are in your home.

Best Hardwired: Kidde Smoke and Carbon Monoxide Detector, Hardwired with Lithium Battery and Interconnect

 Kidde Smoke Detector, Hardwired Smoke Alarm with Lithium Battery Backup

Power Source: Hardwired with battery backup | Sensor Type: Ionization | Pack Size: Single

What We Like
  • Smoke and Carbon Monoxide Detection

  • Hardwired and lithium battery back up

  • Interconnectability

What We Don't Like
  • Professional installation required

This combination smoke and carbon monoxide detector also has multiple power sources: hardwired and a lithium battery backup. So you never have to worry about losing power or needing to change the batteries, since the installed lithium batteries last for 10 years. You will need professional installation, but this additional setup step means that you can connect up to 24 units into one whole-home system.

Best Battery Operated: First Alert SCO5CN Combination Smoke and Carbon Monoxide Alarm

First Alert SCO5CN Combination Smoke and Carbon Monoxide Detector

Power Source: Battery operated | Sensor Type: Photoelectric | Pack Size: Single

What We Like
  • Easy installation

  • Easy battery change out

  • Detects smoke and carbon monoxide

What We Don't Like
  • Only one smoke sensor

This battery operated unit is easy to install, has visual and audible alerts, and uses multiple sensors. Whether it detects smoke using its photoelectric sensors or carbon monoxide using its electrochemical sensors, the voice alert will let you know about the danger. The visual panel will light up with either smoke or carbon monoxide, another layer of alert and protection.

It uses two AA batteries, which many homeowners have on hand. Changing the battery is easy with the pop-open panel on the front of the unit. If you do get a low battery alert, you can silence it for up to 8 hours while you change the batteries in the unit.

Best Smart: Google Nest Protect Wired Smoke and Carbon Monoxide Detector

nest-smoke-detector

Power Source: Hardwired or battery | Sensor Type: Photoelectric, ionization, and carbon monoxide | Pack Size: Single

What We Like
  • Hardwired or battery

  • Multiple alerts

  • Silence false alarms from your phone

  • Comprehensive detectors

What We Don't Like
  • Expensive

  • Need other smart devices to take advantage of best features

If you’re willing to spend a little more on a smoke detector, the Nest Protect is a top-rated smart smoke and carbon monoxide alarm. This unit comes in both hardwired and battery-powered models, and it connects to your phone via WiFi to send real-time updates on what’s happening in your house.

The Nest Protect includes a variety of useful features beyond smoke and carbon monoxide detection. This smart product automatically tests itself to save you the hassle, and it sends alerts to your phone whenever it detects a problem, letting you know there’s an emergency even when you’re not home. If there’s a false alarm, you can silence the detector from your phone, and when you walk underneath the unit at night, it lights up to help you see better.

What Testers Say

"Given that our new house is three stories, we opted to create a network of Nest Protects, with one on the ground level and another on the second floor. The volume of the voice messages is clear without being too loud, and communication is broadcast from both devices as well as through the app."—Nathan Borchelt, Product Tester

Best Dual Sensor: First Alert BRK 3120B Hardwired Photoelectric and Ionization Smoke Alarm with Battery Back-Up

First Alert BRK 3120B Hardwired Photoelectric and Ionization Smoke Alarm with Battery Backup

Power Source: Hardwired with battery backup | Sensor Type: Photoelectric and ionization | Pack Size: 1, 3, 6, or 12 pack

What We Like
  • Photoelectric and ionization sensors

  • Hardwired and battery backup

What We Don't Like
  • Professional installation needed

  • No carbon monoxide detection

If you want the ultimate in smoke and fire detection, the BRK 31220B alarm from First Alert monitors with a photoelectric sensor and ionization sensor. This will alert you to both fast-burning and smoldering fires, providing the most comprehensive detection system. It does not include carbon monoxide sensors, so you will need to purchase a separate unit for your home if needed.

Installation is a little bit more complicated, since this is a hardwired alarm. You can be sure that you’ll never miss an alert, however, with both hardwired and battery backup power sources.

Best Multi-Pack: First Alert BRK 9120B-3 Hardwired Smoke and Carbon Monoxide Detector with Battery Backup, 3 Pack

 FIRST ALERT BRK SC9120B-3 Hardwired Smoke and Carbon Monoxide (CO) Detector

Power Source: Hardwired | Sensor Type: Ionization | Pack Size: 3-pack or 6-pack

What We Like
  • Multiple packs available

  • Hardwired with battery backup

  • Combination smoke and carbon monoxide detector

What We Don't Like
  • Only one kind of smoke sensor

  • Professional installation required

Replacing all of the smoke detectors in your home at the same time is a great idea and this 3-pack from First Alert makes it easy. It’s also available as a 6-pack for those outfitting a large home. These are hardwired units, so you’ll need a professional install. Getting them done at the same time may save some costs. They also have a battery backup.

This combination detector monitors for smoke and carbon monoxide, although it does have only one kind of smoke sensor, ionization. It can connect to other First Alert alarms, however, so you can always install a complimentary photoelectric sensor as part of your system for full coverage.

Final Verdict

Our top pick is the Kidde Battery-Operated Combination Smoke/Carbon Monoxide Alarm with Voice Warning (view at Amazon). It’s easy to install, monitors for multiple dangers, and has a voice alarm to alert you to the presence of smoke or carbon monoxide. If you have room in your budget, we also like the Nest Protect Smoke and Carbon Monoxide Alarm (view at Home Depot) for its ability to send alerts to your smartphone remotely. While it is expensive, it is the only smoke detector on the market to offer this feature. The First Alert BRK 9120B-3 Hardwired Smoke and Carbon Monoxide Detector with Battery Backup, 3 Pack (view at Amazon) is another reliable and top performing option that comes in a multipack for whole home protection.

Kidde Battery-Operated Combination Smoke and Carbon Monoxide Alarm
The Spruce / Katie Begley.

The Spruce / Katie Begley

What to Look for in a Smoke Detector

Power

Smoke detectors can be hardwired or battery operated. Many hardwired smoke detectors have a battery backup to ensure that you will never lose power or the protection of your alarms. Batteries can be standard AA or 9V batteries. Some models also have lithium batteries that come installed in the unit itself and last for 10 years without needing to be changed. Most battery operated models are easier to install but do require changing batteries periodically.

Sensor type

Smoke detectors use one of two sensor mechanisms to monitor for smoke in the air: photoelectric or ionization. Photoelectric sensors can detect smoldering, slow-burning fires. Ionization sensors test for fast-burning fires. The most comprehensive smoke detectors have both sensors inside, as well as additional safety monitoring such as carbon monoxide detection.

Lifespan

Whether you have a hardwired or battery operated model, you will eventually need to replace the unit itself. Most have a special alarm that sounds when the detector is at the end of its lifespan. Your user’s manual can tell you specific lifespan expectations, but most are between five and 10 years.

FAQ
  • How do smoke detectors work?

    Ionization smoke alarms have a small amount of radioactive material that ionizes the air around it and are generally more responsive to large flames. When smoke enters the chamber, it disrupts the flow of ions and activates the alarm. Photoelectric alarms on the other hand respond best to smoldering fires. This type of alarm works by using a light sensor. A light source is aimed into a sensor chamber and if smoke enters it, light is reflected and triggers the alarm. You won't be able to predict what kind of fire you may have so you should always have both types of protection in your home for ample safety.

  • How do you change a battery in a smoke detector?

    To change your smoke alarm's battery, you'll need to remove the cover first. Most covers twist open, but for some you'll have to use a screwdriver. Your user's manual should give you specific instructions based on your model, but most are pretty easy to change once you've removed the cover. Simply disconnect the old battery (many use a 9v battery, but some use lithium) and replace it with the new one. Make sure it's firmly into place and facing the correct way.

    Use the test button after installing the new battery to ensure it's correctly installed. If the test alarm doesn't sound, your battery may be facing the wrong way. Mark the inside of the alarm with the date you changed the battery to remind yourself later on. You should also check your alarm's battery at least twice a year to ensure maximum safety around your home.

  • How many smoke detectors do I need?

    According to the NFPA, every level of your home should have a smoke alarm, including your basement. Smoke alarms are the fastest way to indicate a fire and prevent it from further spreading to other rooms of the house so you should have one in each bedroom and one outside every sleeping area. Even if your home already has a set number of hard-wired alarms, you can still place extra ones that are battery operated around the house as well. In the case of fire prevention, it's better to have an extra amount of alarms rather than not enough.

Why Trust The Spruce?

This article was researched and written by Katie Begley, a freelance writer specializing in home and family products. Katie has been writing for The Spruce since 2019. All of the smoke detectors included in this list were chosen for their superior performance, multiple sensors, and installation. Special mention was made for those units that can work as part of a whole-home system or offer extra monitoring of threats like carbon monoxide.

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Article Sources
The Spruce uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Smoke inhalation is the most common cause of death in house fires, Michigan State University Extension.

  2. Ionization vs. photoelectric, National Fire Protection Association.

  3. Changing Clocks and Batteries. National Fire Protection Association

  4. Ionization vs. Photoelectric. National Fire Protection Association.

  5. Installing and Maintaining Smoke Alarms. National Fire Protection Association.