A tall flame burns in front of smoke and carbon monoxide detectors in a Consumer Reports lab.
Our test engineers create tall flames for our flaming fires test to see whether smoke detectors alarm appropriately.

Most smoke and carbon monoxide detectors look the same, so you might think that they basically are the same. As long as they've been certified by a testing organization, such as Underwriters Laboratories (UL), they should work just fine, right? Not exactly.

"We need to test detectors because some fail at CO detection, and there are differences in how quickly different models respond to CO," says Bernie Deitrick, Consumer Reports' test engineer for smoke and CO detectors. "I have never tested a model that failed our fire and smoke tests, and it is reassuring to know that such critical devices actually work."

A detector's ability to sense carbon monoxide can mean the difference between life and death. According to the CDC, more than 400 Americans die from accidental CO poisoning every year.

At Consumer Reports' test labs, we expose detectors to both flaming fires and smoldering, smoky fires to see how well they detect smoke and fire. For CO alarms, we expose them to precise high CO levels (400 parts per million) and low CO levels (100ppm) to see how accurately and how quickly they detect the deadly carbon monoxide. And for stand-alone CO detectors, we also check the accuracy of the CO levels that they either display on their screens or read aloud via voice messages.

Though detectors have differences in performance, there are also big differences in their power sources. Generally, detectors can either be battery-powered, hardwired, or plugged into an outlet. Battery-powered detectors can be placed anywhere and run on replaceable batteries (usually 9-volt or AA) or sealed lithium batteries that last 10 years. Hardwired detectors require special wiring for power that's typically found only in newer or renovated homes. Plug-in detectors receive a constant flow of power from an outlet. Both hardwired and plug-in detectors use a backup battery in the event of an outage that you need to replace annually.

To determine the type you need, remove the detectors in your home from their mounts. If there are wires connected to them that run into the wall or ceiling, then you need hardwired detectors. If there are no wires, then you need battery-powered detectors.

Below are the best smoke and carbon monoxide detectors from our tests. You’ll find stand-alone smoke detectors, stand-alone CO detectors, combination smoke/CO detectors, and smart smoke/CO detectors that can send alerts to your smartphone. There are hardwired and battery-powered picks for each type of detector.

To see all of the models we’ve tested, check out our full smoke and carbon monoxide detector ratings. And for help picking the right types of detectors for your home, see our smoke and carbon monoxide detector buying guide

Best Hardwired Smoke Detectors

First Alert 3120B

    CR’s take: The First Alert 3120B is a dual-sensor smoke detector, meaning it has both a photoelectric sensor for detecting smoky fires and an ionization sensor for detecting flames. Thanks to its use of both types of sensors, this First Alert receives top scores in our flaming fire and smoldering fire tests. It’s hardwired with a battery backup, which makes it a good candidate for newer or remodeled homes that have wiring for detectors, and it features a hush button to silence nuisance alarms. It can be interconnected with additional detectors so that if one goes off, they all go off and alert you to danger even if you’re on a different room or floor than the fire. 

    Kidde PI2010

      CR’s take: Another top performer in our tests is the Kidde PI2010, which receives high scores in our flaming fires and smoldering fires tests. This hardwired, dual-sensor alarm features a battery backup, a hush button, and the ability to interconnect with other compatible detectors. To determine which other models are compatible with this one, check with Kidde.

      Best Battery-Powered Smoke Detectors

      First Alert SA320CN

        CR’s take: The First Alert SA320CN is one of the best battery-powered, dual-sensor detectors in our ratings, receiving high marks in both the flaming fire and smoldering fire tests. It features a hush button and runs on two AA batteries, but it can’t interconnect with other alarms to make them all go off in the event of a fire. 

        Kidde PI9010

          CR’s take: Another good choice for a battery-powered detector: the Kidde PI9010. This top-notch detector receives strong scores in our tests for flaming fires and smoldering fires. It features a hush button and runs on a single 9-volt battery, but it can’t interconnect with other detectors. 

          Best Hardwired Carbon Monoxide Detector

          Kidde Silhouette KN-COPF-1

            CR’s take: The hardwired stand-alone Kidde Silhouette CO detector performs very well. It receives great scores in our high and low CO level tests and a Very Good rating for the accuracy of its CO level display. This model features the ability to log the highest CO levels it detects (referred to as peak memory), which is good for checking whether there was a problem when you’ve been away from home for a long period of time so that you know to have things checked out. It also has a battery backup and the ability to interconnect with other compatible alarms.

            Best Plug-In Carbon Monoxide Detector

            First Alert CO615

              CR’s take: The First Alert CO615 is one of the few plug-in CO detectors in our tests, and it beats out its hardwired and battery-powered brethren, with strong scores in our tests for detecting high and low CO levels quickly, as well as a Very Good rating for the accuracy of its CO level display. It features a battery backup and peak memory (so that you can check whether CO levels were high after you've been gone for a long period of time). 

              Best Battery-Powered Carbon Monoxide Detector

              First Alert CO410

                CR’s take: If you need a battery-powered, stand-alone CO detector, check out the First Alert CO410. It excels in our tests for detecting low CO levels and for how accurate its CO readings are on its display. It also performs very well in our high CO level test, but not as well as in the low CO level test. Aside from its display, this model’s only other feature is peak memory, which logs the highest CO reading so that you can see whether there was a problem while you were away from home. 

                Best Combination Smoke and Carbon Monoxide Detectors

                Universal Security Instruments MIC3510SB

                  CR’s take: The Universal Security Instruments MIC3510SB is one of few combination detectors that has both photoelectric and ionization sensors for smoldering and flaming fires (most combo models have only one of the two) in addition to a CO sensor. As a result, this USI detector is the only combination model to perform well across all of our smoke and CO tests. This model runs on a sealed, 10-year battery. It features a hush button. However, it can’t interconnect with other detectors. 

                  First Alert SC7010B

                    CR’s take: If you need a hardwired combination detector, the First Alert SC7010B is your best bet. It performs well in our CO and smoldering fire tests, though it receives a Poor rating in our flaming fires test. If you decide to go with this detector, you may want to also consider purchasing a battery-powered ionization smoke detector, such as the Kidde RF-SM-DC that receives an Excellent rating in our flaming fires test (if you want a hardwired one, you may have to pay an electrician to install the proper wiring so that it can be placed near the First Alert detector). This First Alert features a hush button, battery backup, and the ability to interconnect with other compatible alarms. 

                    Best Smart Combination Detectors

                    First Alert Smart ZCOMBO-G (1039833)

                      CR’s take: If you want a smoke and CO detector that can send you smartphone alerts when you’re away from home, consider the First Alert Smart ZCOMBO-G. This battery-powered detector performs very well in all except our flaming fires test, for which it receives a Poor rating. If you go with this detector, you may want to also consider purchasing a battery-powered ionization smoke detector, such as the Kidde RF-SM-DC. This First Alert features a hush button, runs on two AA batteries, and can interconnect with other compatible detectors. This model uses a wireless network called Z-Wave, not WiFi, so it requires a third-party smart home hub to connect to the internet and your smartphone. Compatible hubs include Samsung SmartThings, Ring Alarm, and Nexia Home Intelligence. 

                      First Alert Onelink Smart 1042135

                        CR’s take: For a smart smoke/CO detector that connects directly to WiFi, check out the First Alert Onelink Smart 1042135. This model receives strong scores in all of our tests, with the exception of flaming fires because it lacks an ionization sensor. If you go with this detector, you may want to also consider purchasing a battery-powered ionization smoke detector, such as the Kidde RF-SM-DC. This First Alert comes in both battery-powered and hardwired versions, can interconnect with other compatible detectors, and works with Amazon Alexa and Apple HomeKit/Siri for voice control. 

                        Nest Protect: Smoke + Carbon Monoxide

                          CR’s take: The Google Nest Protect is another WiFi-enabled combination smoke/CO detector that performs well in our tests. It receives strong scores in our tests for low CO levels and smoldering fires. It receives a Good rating for detecting high CO levels. But like the First Alert OneLink above, it falls short in our flaming fires test. If you go with this detector, you may want to also consider purchasing a battery-powered ionization smoke detector, such as the Kidde RF-SM-DC. The Google Nest Protect comes in both battery-powered and hardwired versions and can interconnect with additional Nest Protects.