The simplest type of carbon monoxide detectors are easy to buy and install: They either plug into an outlet or use a battery. These units are easy to use and possess sensors that typically last for five to seven years. Overall, we found Kidde and First Alert carbon monoxide (CO) detectors are mentioned most often in reviews.
Users say one highly rated product, the First Alert CO615 (*Est. $35), is easy to install and use. This detector, which plugs into any outlet, has a clear backlit display that shows and stores both current and peak CO levels. In expert tests, this CO detector was the most accurate at registering both high and low CO levels. Should a false alarm be triggered, you can silence it by pointing a TV remote at the detector. This plug-in carbon monoxide detector comes with a battery backup in case of a power failure. The First Alert CO615 also comes with a power cord that gives users the flexibility of placing it on a nearby table or shelf rather than right at the outlet. According to the manufacturer, this detector's electrochemical sensor lasts for five years.
The First Alert CO615 also receives mostly positive reviews from nearly 50 owners at Amazon.com and another handful at Walmart.com. Notably, owners say it doesn't output false alarms or display frequent low-battery alerts like some other CO detectors. One criticism: It won't display the current CO level unless you press a button -- a trait some users say is annoying. Many people find it more reassuring to constantly see a zero displayed. A few owners also complain about the product's battery door, saying it can be difficult to properly close.
The Kidde Nighthawk KN-COPP-3 (*Est. $45) is another plug-in model that has a digital display. Some consumers may feel more at peace with this product since it constantly shows an area's CO level (a button doesn't have to be pressed to see this information). Although this detector performs as well as First Alert in responding to CO levels of 300 parts per million (ppm), it lags behind in professional tests for detecting lower levels of 150 ppm. The manufacturer covers it with a five-year warranty, but says its electrochemical sensor lasts up to seven years, which is two years longer than First Alert.
The Kidde Nighthawk KN-COPP-3 carbon monoxide alarm receives a perfect rating from several owners at Target.com and HomeDepot.com, who say it's been reliable for years. However, reviews are mixed from more than 100 owners at Amazon.com. More than two dozen people give it the lowest rating. Their top complaint: Its 9-volt backup battery drains too quickly and a few people report trouble with false alarms.
The Kidde KN-COPP-B (*Est. $35) is a top-rated choice for people who want a detector that's battery-operated. While that makes it very easy to place (because you don't need to be near an outlet), users need to be diligent about replacing the unit's three AA batteries when its low-battery alert sounds. This model's backlit display shows a continuous CO reading and can switch to provide a peak-level reading by pressing a button. This detector has a five-year limited warranty, and the electrochemical sensor has a seven-year lifespan.
According to one professional review, the response time of this battery-operated Kidde is good overall, but slower than the plug-in models mentioned previously; however, it gets more positive reviews by owners at Amazon.com. Here many say they are generally pleased with its performance and ease of use. A few reviewers do say it didn't work properly, complaining its display started to output unintelligible readings.
If you don't care about a digital display, the Kidde KN-COB-B (*Est. $15) is an inexpensive choice. This detector is about as no-frills as they come; the KN-COB-B has a test button and green LED light to indicate whether it is powered, and it gives an audible alert when its battery needs replacing. According to one professional review, its accuracy is comparable to the Kidde KN-COPP-B. Reviewers posting to Amazon.com say it's easy to install and even comes with three AAA batteries. Still, a few owners complain of unexplained false alarms. Like other Kidde models, this unit comes with a five-year warranty and has a sensor lifespan of seven years (according to the manufacturer).
Combination smoke/CO detectors are appealing for a couple of reasons; first, you only need to worry about changing batteries in a single unit, and second, combining units makes for less clutter. However, there are some drawbacks. There are two types of smoke detectors -- photoelectric, which are better at detecting smoldering fires, and ionization sensors, which are better at sensing high-flaming fires. We cover both types in our report on smoke detectors; in that report, the very best models are those that contain both types of sensors. The problem with combo CO/smoke detectors is that you only get one of the two types of smoke sensors, not both. So, if you want the best protection, you'd still need to install an additional smoke detector.
An example of this type is the battery-powered Kidde KN-COSM-B (*Est. $35), which combines a CO detector with an ionization smoke sensor. Consumers applaud its voice warning system that announces a fire, carbon monoxide or a low battery -- a nice feature when the alarm wakes you during the night so you know exactly what the alarm is for. Visual cues include a green LED for normal operation and a flashing red LED when the alarm goes off. The lack of a digital display showing carbon monoxide levels is the main drawback. The warranty period is five years and the CO sensor lasts for about seven years.
We didn't find any expert reviews of this Kidde combination detector, but it gets pretty good ratings from owners. At Amazon.com, more than 70 owners give it a rating of 4.2 stars out of 5. The majority say it's reliable, loud and installs easily, but a few express concern that it didn't sound an alarm when smoke was present. It gets an even higher rating of 4.7 out of 5 at HomeDepot.com and Lowes.com; owners there like its voice feature, and several say they were saved by the detector sounding an alert when fire or carbon monoxide was present.
In bigger homes or homes with several floors, installing interconnecting CO detectors is an alternative to installing several standalones. With these devices, if one interconnected detector goes off, it will trigger all other alarms, alerting the whole house to danger. Interconnecting carbon monoxide detectors either connect using existing wiring in the home or are battery operated and work wirelessly using radio frequency. Hardwired detectors should be installed by a licensed electrician to ensure they are working properly, while wireless detectors can be installed without professional help.
If you're looking for the more do-it-yourself solution, the First Alert Onelink SCO501CN (*Est. $75) is pricey, but since it's battery powered, you can install it yourself. Each alarm can be connected to up to 15 other detectors. This detector is the top-rated interconnectable CO detector in one professional review that compares response time to both low and high levels of carbon monoxide. In addition to a CO detector, the First Alert Onelink also includes a photoelectric fire sensor. Although this detector lacks a digital display, it announces peak CO levels stored in memory with a touch of a button. It operates on two AA batteries and is covered under a five-year limited warranty.
At Amazon.com, two dozen owners contribute to an average rating of 4.1 stars out of 5 for the Onelink detector. Reviewers appreciate the versatility of its voice alarm, which can be preprogrammed to shout out the location of the danger (saying things like "basement" or "bathroom") as well as the problem ("carbon monoxide" or "fire"). Several owners also say it doesn't plague them with false alarms like other detectors. This unit has an internal timer and gives an alert when its sensor's six-year lifespan expires. Among the complaints we read were that the batteries don't last very long in the units (though most say they last a year). And a few people complain that the price is so high that it makes no sense to buy this sensor unless you plan to buy several and connect them.
If your home is pre-wired for detectors, the Kidde AC Wire-in Combination Carbon Monoxide & Smoke Alarm KN-COSM-IB (*Est. $45) is an electrical carbon monoxide and smoke detector with a battery backup. Experts give it good marks for detecting CO, but say it doesn't respond quite as quickly as the First Alert Onelink. Like the standalone Kidde AC KN-COSM-B detector, it has an ionization sensor for detecting flames (but not a photoelectric sensor for detecting smoldering fires). After its horn alarm sounds, a voice alarm announces the type of emergency (fire, carbon monoxide or low battery). Owners at Amazon.com give it an average rating of 4.2 stars out of 5 and report few false alarms.
The Kidde Silhouette KN-COPF-I (*Est. $70) is a CO-only detector that has good response times to high and low levels of CO in one expert review. It's a more expensive, hardwired model, but it has a digital display that helps occupants to monitor rising CO levels even before an alarm sounds. It also has an extremely low profile that makes it look less obtrusive on a wall. Although we didn't find owner reviews on this model, consumers will appreciate the self-charging lithium backup battery that never needs replacing. The manufacturer says this detector can connect with up to 23 other Kidde detectors and that the sensor lasts for seven years. This model is covered under a five-year warranty.