The Best Carbon Monoxide Detectors for the Home

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Best Carbon Monoxide Detector


No home safety plan is complete if it doesn’t include carbon monoxide detectors. When they detect the presence of carbon monoxide—a colorless, odorless, and poisonous gas—these devices emit a shrill alarm, just like a smoke detector. In fact, some of the best carbon monoxide detectors serve the dual purpose of helping protect your home against both carbon monoxide and fire. Ahead, get tips on navigating and differentiating between the available options—and don’t miss our top picks, below.

  1. BEST OVERALL: Kidde Carbon Monoxide and Explosive Gas Detector
  2. BEST VALUE: Kidde Carbon Monoxide Alarm
  3. UPGRADE PICK: Kidde Hardwire Carbon Monoxide Detector Alarm
  4. TECH PICK: Google Nest Protect

Carbon Monoxide and How It’s Detected

Carbon monoxide (CO) is generally a by-product of combustion: Any appliance that uses a fuel source (a water heater, furnace, or boiler, for example) produces carbon monoxide when it’s running. That excess carbon monoxide is meant to be released outside through chimneys and vents. These appliances are extremely safe when working properly, but when something goes wrong, the carbon monoxide can build up to dangerous levels.

Carbon monoxide is measured in parts-per-million (or PPM). Exposure of 50 PPM is safe for up to eight hours, 150 PPM is dangerous after 50 minutes, and 1,600 PPM can kill a healthy adult in less than one hour. Carbon monoxide detectors are so important because the gas is colorless and odorless, and homeowners won’t be able to detect it on their own until it’s too late. Carbon monoxide detectors track levels of the gas over time and sound the alarm when those levels exceed certain parameters. For instance, a 50 PPM measurement will activate most alarms after 8 hours, 150 PPM within 50 minutes, and 400 PPM within 15 minutes.

Detector Locations

The general consensus is that a carbon monoxide detector should be installed on every floor and either in or outside of every bedroom. One should be placed in the basement and the garage as well.

Testing Intervals

When it comes to ensuring proper operation, homeowners should follow the same guidelines they use for their smoke detectors. Carbon monoxide detectors should be tested monthly, and batteries should be replaced at least once a year, regardless of whether the low battery alarm sounds.

Device Lifespan

Even if the batteries in a carbon monoxide detector are changed regularly, the detectors themselves don’t last forever. Check the back of your devices to find out what their expected lifespan is. This number is usually between five and seven years. If you can’t remember when you purchased the device, you should consider replacing it.

The Best Carbon Monoxide Detector Options


Types of Carbon Monoxide Detectors

There are two types of carbon monoxide detectors available on the market: stand-alone and combination models. Choosing the correct type for your home depends on several factors.

Standalone Carbon Monoxide Detectors

A stand-alone carbon monoxide detector’s only job is to detect and measure the levels of carbon monoxide in the home. Battery-operated models can be placed nearly anywhere and they are the more popular choice. For a more stationary placement, choose a plug-in style detector. These models often have digital read-outs that display the current level of carbon monoxide being detected.

Combination Carbon Monoxide Detectors

Combination units are multi-purpose, monitoring carbon monoxide levels while also detecting smoke or explosive gases. The benefit of combination units is that they take a lot of the planning and guesswork out of building your fire safety system. The downfall is that for optimal use, combination carbon monoxide detectors shouldn’t be placed close to gas or oil-fired appliances. In that situation, a stand-alone smoke detector is best with a separate stand-alone carbon monoxide installed further away.

Contrary to popular belief, a carbon monoxide detector alone will not detect the presence of explosive gases. Explosive gases don’t contain carbon monoxide unless they’re accompanied by burnt fuel. Carbon monoxide detectors with explosive gas detection capabilities will pick up on these gases, however, and alert you to their presence.

Key Shopping Considerations

Consider the following features to select the best carbon monoxide detector on the market today.

Battery-Powered, Plug-In, or Hard-Wired?

Carbon monoxide detectors can be purchased with a few different power supply options.

  • Battery-powered options are great for placing anywhere in the home. They don’t require any outlets or pre-existing wiring. For example, having an easy-to-install battery-powered unit in a garage workshop that uses propane heat is an excellent idea.
  • Plug-in models require an outlet. This drastically reduces the flexibility of installation but they do have battery backups. Plug-in units are great for extra protection in areas that already include smoke detectors.
  • Hard-wired models use pre-existing fire alarm wiring and battery back-ups for their power source. Hard-wired units are the most desirable and should be used wherever possible, but not every home has fire alarm-specific wiring run to every room.

Depending on the situation, a comprehensive system could include units from all three categories.

UL Listing

Just like the best smoke detectors, carbon monoxide detectors need to be listed by Underwriters Laboratories. The UL listing on the back of the unit shows that the unit’s design was tested and passed UL’s stringent requirements. As important as carbon monoxide detection is, UL-listed models should be the only ones you consider purchasing.

Digital Displays

Digital displays may seem like a gimmick but they actually serve a fairly important purpose. These units will display the PPM of any amount of carbon monoxide they detect, even if they don’t go into alarm mode. This can help a homeowner determine if there is more baseline carbon monoxide in their home than they thought—a feature a standard carbon monoxide detector won’t offer.


Carbon monoxide detectors that can be programmed or wired with other alarm devices in the home through radio-frequency, Wi-Fi, or direct wiring are considered interconnect-capable units.

With homes rapidly becoming more connected and smart, interconnect-capable units can be an added benefit for the homeowner already comfortable with linking their systems together. For example, an interconnected carbon monoxide activation in the garage will trigger other alarm devices in the home. This will alert the occupants no matter where they are in the home. If the device reports back to a central monitoring station, an alarm company will notify first responders and send help without you even picking up the phone. This can be an especially huge benefit at night, when a homeowner might not hear the garage alarm sound from the other end of the home, and when symptoms of carbon monoxide poisoning are less likely to be noticed.

Smart Features

In a world where appliances like faucets and refrigerators are smart, why shouldn’t there be smart home safety devices? Smart carbon monoxide detectors typically offer a combination of carbon monoxide and smoke detection and can communicate alerts to a smartphone app, base station, or full-fledged smart-home system. They can be programmed to describe the area and type of device that’s been activated. They can also provide real-time condition updates to an app like room temperature.

Our Top Picks

Best Overall

The Best Carbon Monoxide Detector Option: Kidde Plug-In CO and Explosive Gas Detector

This Kidde carbon monoxide detector does more than just sniff out dangerous levels of carbon monoxide. This plug-in model (with a battery backup) can also detect the presence of explosive gases. The digital display alerts you to the real-time carbon monoxide levels in your home while the peak level function shows the highest point reached since it was last reset. It can be plugged directly into an outlet or with the included corded adapter. Users should note that explosive gas detection is not immediate: occupants will probably smell the gas before the detector goes off if they’re awake, but it’s a great extra feature.

Best Value

The Best Carbon Monoxide Detector Option: Kidde Battery-Operated CO Detector w/Digital Display

If you’re looking for a fully capable carbon monoxide detector at a budget-friendly price, this model from Kidde may fit the bill. Despite its low price, it has most of the features of a more expensive unit: digital read-out, a peak button, a silence and reset button, as well as LED bulbs to signal the status of the system (green for normal, red for alarm). This model uses three AA batteries, so it can be mounted on a wall or placed on a countertop or nightstand. What it can’t do is communicate with other devices.

Upgrade Pick

The Best Carbon Monoxide Detector Option: Kidde Hardwire CO Detector Alarm with Battery Backup

Some homes come with fire alarm wiring, while others have been retrofitted to meet local codes. In those cases, this Kidde carbon monoxide detector is a great way to go. While this isn’t a combination model, it is interconnect-capable so it will communicate with other devices that are hardwired into the system. It also uses a 9V battery back-up for continuous protection when the power goes out.

Keep compatibility in mind. This unit can be hardwired into any system and will function independently, but its interconnectivity is limited to other Kidde fire alarm devices.

Tech Pick

The Best Carbon Monoxide Detector Option: Nest Protect Smoke and Carbon Monoxide Alarm

The Google Nest Protect is a great pick for smart home aficionados. This model detects both smoke and carbon monoxide and can alert you to a problem even if you aren’t home. When the Nest activates, it sends an alert to your app, your smart home system, and central monitoring company through your Wi-Fi network. Being interconnect-capable, it will also activate other smart alarm devices in the home. For the latest in features and capabilities, however, you need to keep your apps updated.