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    Smoke & Carbon Monoxide Detector Buying Guide

    Smoke & Carbon Monoxide Detector Buying Guide

    Installing and maintaining smoke and carbon monoxide (CO) detectors can save your life. Luckily, they’re inexpensive and easy to install. Basic smoke detectors cost as little as $10, and carbon monoxide detectors cost as little as $20.

    Newer models offer more features. For example, interconnected detectors communicate among devices and provide integrated, whole-house protection. With such a system, when one detects smoke or carbon monoxide, all of them will sound—whether the detectors are hardwired or wirelessly connected.

    How We Test Smoke and Carbon Monoxide Detectors

    Each smoke and carbon monoxide detector that enters Consumer Reports’ labs is rigorously tested to make sure it keeps you and your family safe. For smoke detectors, we test response time to both flaming fires and smoky, smoldering fires. We’ve found that not all detectors can adequately detect both fire types.

    We test carbon monoxide detectors against low CO levels (100 parts per million) and high CO levels (400 ppm). We also test the accuracy of their carbon monoxide measurements if they offer readings through a digital display or audio announcements.

    Combination detectors go through both sets of tests. All these test results are then folded into our comprehensive smoke and carbon monoxide detector ratings

    Types of Smoke and Carbon Monoxide Detectors

    You can find standalone smoke detectors and carbon monoxide detectors, as well as combination smoke and carbon monoxide detectors in smart and non-internet-connected forms. All three detector types offer standalone and interconnected varieties. Few combination detectors are effective at detecting carbon monoxide, smoldering fires, and flaming fires, which is why we recommend that consumers use a combination of detectors in their homes for complete protection. 

    Smoke Detectors

    Smoke Detectors

    Fires burn differently: Some flare, some smolder. You’ll find three types of smoke detectors on the market, but only one is effective against both types of fire.

    Ionization smoke detectors are best at detecting the small particles typical of fast, flaming fires. But in our tests, all tested poorly for detecting smoky, smoldering fires. Ionization units are prone to false alarms from burnt food and steam, so don’t mount them near a kitchen or bathroom.

    Photoelectric smoke detectors are best at detecting the large particles typical of smoky, smoldering fires but poor at detecting fast, flaming fires. Photoelectric units are less prone to false alarms from burnt food, so they may be a better fit in kitchen areas.

    Dual-sensor smoke detectors combine ionization and photoelectric technology to detect both flaming and smoldering fires, offering you the best protection and saving you the hassle of installing two separate smoke detectors. But you may still need to install carbon monoxide detectors, if appropriate for your home.

    Smoke Detectors Ratings
    Carbon Monoxide Detectors

    Carbon Monoxide Detectors

    Carbon monoxide detectors use sensors to detect the presence of CO in your home. Some models include digital displays to show the level of CO they detect, and some can read out the CO level via audio announcements. Remember, carbon monoxide detectors do not detect smoke or explosive gases, such as natural gas, propane, and methane.

    Carbon Monoxide Detectors Ratings
    Combination Smoke & Carbon Monoxide Detectors

    Combination Smoke & Carbon Monoxide Detectors

    Combination detectors incorporate ionization or photoelectric technologies (a few use both) and carbon monoxide detection to protect against both smoke and CO. Both conventional (not internet-connected) and smart models are available.

    Smart detectors offer additional features through a companion smartphone app. Features include smartphone alerts about smoke or CO (even when you’re not home) and low batteries, as well as the ability to hush alarms from your phone. Some models connect to the internet via WiFi; others require an additional bridge or hub, a standalone device that connects smart home products to the internet.

    Combination Smoke & Carbon Monoxide Detectors Ratings

    How Many Smoke and CO Detectors Do I Need?

    Smoke detectors are a must in all homes, and carbon monoxide detectors are needed for any home with fuel-burning appliances, such as a furnace, water heater, range, cooktop, or grill. Even those living in all-electric homes should install carbon monoxide detectors because CO can seep into the house from an attached garage or if a backup generator is used too close to your living quarters during a power outage.

    You’ll need smoke detectors that detect flaming and smoldering fires for each bedroom, one outside each sleeping area, and at least one detector installed on each floor, including in a finished attic and in the basement. You should also have a carbon monoxide detector on each living level, outside each sleeping area, in the basement, and near (not inside) an attached garage.

    Use the illustration below as a guide to where you need detectors, and tally up the number of smoke and carbon monoxide detectors you need to buy. Keep in mind that your home might need more or fewer detectors, depending on its size and number of rooms.

    Smoke and CO detector placement

    Chris Philpot Chris Philpot

    How to Shop for Detectors

    1. Check Local Regulations
    Before you shop, check regulations in your area. Your town or state might have specific requirements (you’ll need to know, say, when you sell your home) about what to use, including types of detectors and their placement. Also, some insurance companies offer a discount for homes with smoke detectors.

    2. Pick a Power Source
    Hardwired smoke and carbon monoxide detectors tie into your home’s wiring—professional installation is required—and usually have backup batteries. Battery-only detectors are the simplest to install, and they work during a power failure. Some models use removable batteries that require annual replacement, while others use sealed lithium batteries that last the life of the detector. Plug-in detectors are also available, but electrical outlets are typically located low on the wall, while the optimal placement for the detector is on or near the ceiling.

    3. Decide on Smart or Not
    Smart smoke and carbon monoxide detectors give you the advantage of knowing if something’s wrong when you’re not home, but they also come with a big price tag. We also haven’t found a smart smoke and CO detector that successfully does it all. But if you decide to outfit your home with this type, we recommend also installing additional dual-sensor smoke detectors. Smart detectors, whether hardwired or battery-powered, will also interconnect with other detectors of the same model. There aren’t many smart models on the market, but we expect that to change when smoke and CO detectors become part of the new Matter smart home standard.

    4. Look for the UL Certified Stamp
    Check the detector packaging for a UL Certified label, to make sure it has passed UL Solutions testing. You should also look for the date of manufacture printed on the back of the detector. Devices lose their sensitivity over time, so the fresher, the better. As a general rule, replace carbon monoxide detectors every five years and smoke detectors every 10 years.

    UL Standards & Engagement, the branch of the former Underwriters Laboratories that focuses on setting standards, has also announced updates to its standards, which will require all manufacturers to make smoke detectors that can distinguish between smoldering fires and cooking smoke. It was originally supposed to go into effect by the end of June 2021, but it has been delayed twice because of supply chain issues, with a new effective date of June 30, 2024. As part of UL Standards & Engagement’s updated standard, it is expected that manufacturers will no longer be able to make traditional single-sensor (photoelectric or ionization) smoke detectors.

    5. Know the Truth About Interconnected Detectors
    You can interconnect some smoke and carbon monoxide detectors so that all units in the house sound an alarm when any single one is triggered. Some newer homes may have wiring already in place to link the detectors. In a home without such wiring, you can buy detectors that interconnect wirelessly. These interconnected smoke and carbon monoxide detectors are an important safety feature in a home with multiple levels, although standalone detectors may be adequate for a small, single-level home.

    While interconnected alarms can make your home safer, they have some limitations. In many cases interconnected alarms can interconnect only with models made by the same brand. In fact, Richard Roux, the National Fire Protection Association’s senior electrical specialist, told CR that you should always check with the manufacturer to see which specific models are compatible, even within the same brand, because some brands could change their interconnect system over time.

    Despite the limitations, we recommend using interconnected detectors. They can make your home much safer by alerting you to danger before the fire or CO spreads throughout your home. Roux adds that interconnected alarms (whether hardwired or wireless) are also becoming a requirement in many states when homes are put on the market.

    6. Consider Voice Alerts
    Children tend to sleep more deeply than adults and might not awaken to a conventional alarm. Some smoke detectors and combination smoke and carbon monoxide detectors use a voice command, but whether that’s the most effective way to wake children hasn’t been determined. According to one study, a greater percentage of children ages 6 through 12 awoke to the sound of their mother’s prerecorded voice than to a tone alarm.

    7. Consider Your Security System
    You can incorporate some smoke and carbon monoxide detectors into a security system that sounds an alarm outside and inside the house. Some systems, such as Ring Alarm, even let you keep your existing detectors by adding an alarm listening device, which triggers the security system when it "hears" your detectors go off. Such systems may also have a monitoring service that can notify the police or fire department, or even call your cell phone.

    Installation and Maintenance

    Smoke and carbon monoxide detectors are protective only when installed correctly and if their batteries are replaced annually (unless they have a 10-year sealed lithium battery). Smoke rises, so mount smoke detectors on the ceiling or 12 inches below the ceiling on a wall. Test smoke and carbon monoxide detectors weekly, and vacuum them monthly. Follow the manufacturer’s recommendations regarding battery replacement. Replace carbon monoxide detectors every five years and smoke detectors every 10 years. 

    Smoke & Carbon Monoxide Detector Brands

    First Alert, which was recently acquired by Resideo (maker of Honeywell Home products), owns the BRK-branded units and the Onelink line of wireless, talking units. Products include plug-in, battery, and hardwired units, as well as hardwired units with battery backup. First Alert also makes units that detect carbon monoxide and smoke, and dual-sensor units, which combine ionization and photoelectric technologies.

    Kidde owns Firex-branded units and offers the Nighthawk and Silhouette lines. Nighthawk comes in plug-in and battery-operated units. The Silhouette line comes in hardwired units and features a sealed, self-charging lithium battery that lasts for the life of the unit. Kidde offers combo units, which have a smoke detector feature in addition to the carbon monoxide detector. Kidde also makes dual-sensor units that use ionization and photoelectric technologies.

    The main manufacturers of smoke detectors and CO alarms are First Alert and Kidde, representing three-quarters of the market. Other manufacturers include Code One, Gentex, Google Nest, Honeywell, Panasonic, Swann, and Universal Security Instruments.