What are the regulations in your state or municipality? Most states require a carbon monoxide detector to be installed in new homes or before the sale of a home. Some require hardwired or plug-in units to have battery backup in the case of a power outage -- and having a battery back-up is a good idea in all cases. The National Conference of State Legislatures is a good resource for determining what regulations apply to you.
How are your current carbon monoxide detectors installed? Detectors may be hardwired, plugged into an outlet, or battery operated, depending on the model. Most plug-in and hardwired units use batteries as a backup during a power failure and will not operate if they are not installed. An interconnected system provides the best protection for a typical home. Most interconnected alarms are hardwired, but battery-powered interconnected systems that communicate over a radio network are also available, and are easier for homeowners to install. That said, if your current carbon monoxide detectors are hardwired, you will most likely want to keep that system.
Do you need a smoke alarm, too? If you also need a smoke alarm, opting for a combination smoke and carbon monoxide alarm can save money and clutter. Be aware, however, that some installation locations are more suitable for one type of alarm but not for another. Smoke alarms also use different technologies to detect different types of fires -- ionization, photoelectric, or both. We discuss different types of smoke detectors -- and which ones are best for certain situations -- in our smoke detectors report.
How many alarms do you need? CO alarms should be installed in a central location outside each sleeping area and on every level of the home, according to the National Fire Protection Association, which also recommends interconnecting all alarms.
Does your unit meet safety standards? Check to see that the detector is certified by an independent testing agency such as Underwriters Laboratories or Canadian Standards Association.
Nest was first to market with a "smart" CO and smoke detector, but it won't be the last -- not with the buzz surrounding the so-called "Internet of things." At the January 2015 CES, First Alert announced a competing line of smart devices, including the First Alert DC10-500 Onelink Wi-Fi Smoke and Carbon Monoxide Alarm (Est. $110). The interconnected system uses Bluetooth to communicate, and can send an alert out to an iOS (only, no Android support was announced) app, that can call emergency services on your behalf. The app can also be used to remotely silence false alarms. The DC10-500 is battery operated, and is powered by a sealed 10-year battery that's designed to last for the lifetime of the alarm. The First Alert AC10-500 OnLink Wi-Fi Smoke and Carbon Monoxide Detector (Est. $120) is hardwired to work with any existing hardwired alarms.
Elsewhere in this report:
Best Reviewed Carbon Monoxide Detectors: Hardwired or battery operated, interconnected or stand-alone, CO only or CO and smoke, these are the carbon monoxide alarms that experts and users say are the very best.
The Dangers of CO: What is carbon monoxide, and why do you need to be worried about it?. Our editors lay out the facts and explain how to effectively protect yourself and your loved ones from this silent, deadly threat.
Best Carbon Monoxide Detectors: Whether you want a simple alarm for your bedroom, or to put together a system that can alert you to danger in any room, these are the top CO-only alarms.
Best CO and Smoke Detectors: If you need a detector for both smoke and carbon monoxide, these all-in-one alarms can reduce clutter and save money. Smart combination detectors that connect to the Internet are discussed, too.
Our Sources: Where can you learn more about CO detectors? These are the expert and user reviews we consulted to find the top stand-alone and combination CO detectors.