“Carbon monoxide is known as a ‘silent’ killer because humans are unable to see, smell, or taste it,” says Kelly Johnson-Arbor, the Interim Executive Director of the National Capital Poison Center and a medical toxicologist. She points out that a working carbon monoxide detector emits a loud, obnoxious noise in the presence of dangerous levels of carbon monoxide: “The noise is loud enough to wake up a sleeping individual who might otherwise not experience any warning signs of carbon monoxide poisoning.” We researched the best options available for carbon monoxide alarms, including hardwired, plug-in, and battery-powered options. Each model was evaluated based on its safety features, along with how easy it is to install and use, its display options, and overall value. Our top recommendation, the Kidde Nighthawk Carbon Monoxide Detector, impressed with its ease of use, reliability, and affordable price point. Here are the best carbon monoxide alarms.
This plug-in model requires no electrical know-how and takes up just one standard outlet. Once it powers on for the first time, it lasts for 10 years before signaling it’s time for replacement. A 9-volt battery backup gives you confidence that the Kidde Nighthawk keeps monitoring for carbon monoxide, even if there is a power outage. The Kidde Nighthawk also stands out for having a simple interface. It has just two buttons: for testing the unit and to recall peak levels of detected carbon monoxide (CO), measured in parts per million (PPM). The digital display is a helpful feature not always found on carbon monoxide detectors. It provides a reading of current CO levels and is helpful for interpreting the beeps that the device may emit. The intermittent pattern of the alarm—four beeps, followed by 5 seconds of silence—may not immediately grab your attention. However, it is loud enough that we feel confident it would wake most people while sleeping. “The volume definitely gets your attention,” our at-home tester reported. “There were children in another room, and they were on high alert once the alarm started sounding.” Dr. Johnson-Arbor suggests that carbon monoxide detectors should always be placed in or within 10 feet of any sleeping area. With this parameter in mind, the Kidde Nighthawk is an excellent choice. Price at time of publish: $34 The First Alert Battery-Operated Carbon Monoxide Detector uses a proven form of detection in the form of an electrochemical sensor. The unit is powered only by a 9-volt battery, so you’re not limited on where to place the carbon monoxide detector because of outlet proximity or electrical wire connections. While this product represents a good value, it’s worth noting that it should be replaced every 5 years, while some other models offer a 10-year life expectancy. An end-of-life signal chirp and low-battery beep round out the features of this simple unit. Price at time of publish: $42 Like most similar products, this Kidde model includes a battery backup for uninterrupted monitoring, even if the power supply is interrupted. It requires two AA batteries, which you may be more likely to have on hand than the 9-volt battery backup some other plug-in carbon monoxide detectors require. Whether the unit is running on electricity or battery power, an 85-decibel alarm sounds if it detects carbon monoxide levels exceeding safe levels. This basic model lacks a digital display, so you need to consult the owner’s manual to learn what the small color-coded light signals mean. The light glows green during normal operation but turns red because of an alarm, low battery power, or the end of the unit’s life span. Price at time of publish: $30 There are plenty more user-friendly features built into this smoke and carbon monoxide detector that integrates with Google Assistant, but the safety benefits are the most important. While virtually all carbon monoxide detectors include a testing function, it’s easy to skip out on actually performing a test to ensure that your unit is operating properly. The Nest Protect is designed to silently test its batteries and sensors more than 400 times each day. Once a month, it tests the audible alarm functions by sounding the speaker and horn within the unit. Before bed each night, you see the light ring around the center of the unit turn green to indicate that the battery level is sufficient and assure you won’t be woken up to an unpleasant low-battery alarm. If smoke or carbon monoxide levels become dangerous, the device alternates between an audible alarm and a voice alert specifying where the problem originates from. The center ring of the Nest Protect also glows red to give you a visual indicator there is an emergency. Nest Protect is available as a battery-operated or hardwired unit. We prefer the hardwire option because all the features and functions of this smart carbon monoxide detector can drain battery power. So it’s not surprising that the battery version requires 6 AA cells. (The hardwired version needs 3 AA batteries for its backup power system.) The sensors inside this combo smoke and carbon monoxide detector have a 10-year life span, which is good to know if you’re installing the unit in a state that regulates the life expectancy of smoke detectors. However, it’s worth noting that the manufacturer’s warranty on the unit is only valid for 2 years. Price at time of publish: $117
The First Alert CO5120BN’s electrochemical sensor detects carbon monoxide levels over 30 parts per million. (Symptoms become more noticeable over 70 ppm.) When the concentration exceeds safety thresholds, it triggers an 85-decibel alarm. The only other warning is a small red light, which flashes in a special pattern when the detector is triggered. The light keeps flashing, even when CO drops below hazard levels. So you need to manually clear the latching alarm by testing the unit. Price at time of publish: $32 This combo smoke and carbon monoxide detector uses 2 AA batteries. It’s rated for 10 years of use, making it compliant even in states that require a 10-year lifespan for smoke detectors. It’s also worth noting that the Kidde Smoke & Carbon Monoxide Detector uses an ionization sensor, which is likely to register a fast-burning fire more quickly than a product using a photoelectric sensor to detect flaming and smoldering fires. If cooking or other activities initiate a false fire alarm, as happened with our at-home tester, this device’s Smart Hush feature silences the alarm for 8 minutes, giving you an opportunity to clear smoke from your cooking mishap or your extinguished candle. Price at time of publish: $45 However, we recommend this compact carbon monoxide detector for the information it provides, via an easy-to-read LCD screen. It displays detected CO in parts per million (PPM), along with a battery status indicator, so you’re not caught by surprise when the battery power runs low. Fortunately, the 5-year lithium-ion battery offers long life and shouldn’t require frequent replacement during the unit’s expected 10-year life span. A handy feature is the Peak CO Concentration Memory. Press this button and the display shows you the highest detected levels of carbon monoxide. Also enhancing the visual cues, a color-coded LCD status bar sits just below the digital display. As a portable carbon monoxide alarm, keep in mind that this unit is functional only in ambient air temperatures from 40 and 100 degrees Fahrenheit. While that’s unlikely to be a problem in your house, it may not be functional if deployed in a garage, shed, or other unheated or uncooled structure. Price at time of publish: $40 Many battery-powered carbon monoxide alarms operate using AA or 9-volt batteries that require occasional replacement. However, this popular model from First Alert comes equipped with a lithium-ion battery that is designed to last for the 10-year life span of the unit. The long-lasting battery ensures that the carbon monoxide detector stays on alert at all times, as well as powers the digital display. Some display features worth noting include that it displays CO in parts per million, along with a graphical rendition of the relative concentration level. A peak CO memory function also notifies you of the highest detected levels. It even includes an ambient temperature reading which, frankly, adds no functionality but is nice to have. Price at time of publish: $45 The concept behind the First Alert OneLink Safe & Sound is to combine functional benefits with consistent monitoring of carbon monoxide and smoke levels. The voice-controlled carbon monoxide detector belts out music or podcasts from its speaker, using a Bluetooth connection to your smart device. You can tell Alexa to start or stop playing audio, or use the hands-free technology to control other aspects of your smart home. You also can customize the intensity and color of the built-in light—a handy night light for hallways and other areas. A smart function that’s safety-related is this model’s ability to send an alert to your smartphone if it detects a threat from carbon monoxide or smoke. This means you have an instant heads up wherever you are—in the backyard, at the office, or away on vacation, when a potentially dangerous situation has developed at home. Price at time of publish: $278 Despite the compact size, this carbon monoxide detector is equipped with a standard 85-decibel alarm that is plenty loud enough to alert you if elevated levels of CO are present. In addition, a flashing LED light gives a visual heads-up that the unit is operating as expected (green light) or if an alarm is active (red light). There are few other features to note on this basic device, but it operates in a straightforward manner and has a 10-year life span. Price at time of publish: $48 This hardwired carbon monoxide detector can interconnect with other Gentex devices equipped with the brand’s Dualink technology. In the event of a power outage, it remains operational with the help of a 9-volt battery backup. A self-test button on the front of the unit ensures that it’s working properly. It only has a 5-year lifespan, so you have to replace the unit more often than similar products. But it has a reputation for offering reliable performance with few false alarms. Price at time of publish: $40
Power Source
The power source of a carbon monoxide detector dictates its placement options and how easy it is to install. A hardwired carbon monoxide alarm ties into your home’s electrical grid but uses a battery backup in the event of a power failure. This is the most advanced type of carbon monoxide detector to install, especially if you don’t have an existing hardwired connection. Carbon monoxide detectors with plug-in or battery power sources are the easiest to install. Plug-in models draw power from standard electrical outlets. Like hardwired carbon monoxide detectors, they usually have installed batteries as alternative power supply sources. Battery-only carbon monoxide detectors are also sometimes referred to as portable models. They are ideal for travel or to use in a room where installation or plug-in of a carbon monoxide detector isn’t feasible.
Display
Many carbon monoxide detectors have no display. However, most units have small lights that glow or blink steadily to indicate normal operation, an error, or an alarm. If you want more information from a carbon monoxide detector, you can search out a model with a display that gives you a reading of carbon monoxide levels in parts per million, display highest recorded levels or carbon monoxide, give you battery life status updates, and even indicate the room air temperature.
Interconnectivity
Interconnectivity refers to a carbon monoxide detector’s ability to connect to other home safety monitoring devices such as other CO detectors or smoke detectors. All interconnected carbon monoxide detectors sound when one device detects dangerous CO levels. Interconnectivity of carbon monoxide detectors is a legal requirement in some states. When shopping for interconnected carbon monoxide detectors, keep in mind that compatibility is not universal among all devices across all brands. Check the requirements for any existing carbon monoxide or smoke detectors you have installed; then look for carbon monoxide alarms with compatible interconnectivity. You should also look for devices that have latching alarms. They indicate which carbon monoxide detector set off the alarm, which can be helpful in finding the source of a CO leak.
Sensors and Sensitivity
Carbon monoxide detectors use electrochemical sensors to detect the presence of the colorless, odorless gas. A carbon monoxide detector’s sensitivity should align with Underwriter’s Laboratory (UL) safety standards. These specify that a carbon monoxide detector should alert you within 15 minutes if CO levels reach 400 PPM; within 35 minutes if CO levels reach 200 PPM; and within 90 minutes for CO levels that reach 100 PPM. A carbon monoxide alarm sensor can become damaged by particles in the air. For this reason, Kelly Johnson-Arbor, the Interim Executive Director of the National Capital Poison Center and a medical toxicologist, provides the following caution: “Carbon monoxide detectors should not be installed in furnace rooms, as the detector’s sensor can be clogged or damaged by microscopic particles emitted from the furnace.”
Sound
Carbon monoxide detectors are equipped with audible alarms that sound at a volume of 85 decibels. However some models also include voice alarms. These function depending on the device, but they may announce the danger or specify the location where the threat was detected.
Why Trust The Spruce?
This article was researched and written by Erica Puisis, a freelance writer specializing in home products and appliances. When researching picks for this list, she compared various types of carbon monoxide alarms, including options with and without smoke detection. She evaluated the most popular models based on the power source, display options, and any additional safety or smart home functions.
Many appliances that burn fuel, including water heaters, furnaces, and dryers, pose no threat when operating normally. But they may leak carbon monoxide if their vent or exhaust systems become blocked. It’s important to regularly maintain and monitor those appliances and install carbon monoxide detectors nearby to warn if a leak is detected. As part of the research process, Erica also interviewed Dr. Kelly Johnson-Arbor, Co-Medical Director and Interim Executive Director of the National Capital Poison Center. Dr. Johnson-Arbor shared information regarding the importance of having and installing carbon monoxide detectors in the home.
