How to Buy a Carbon Monoxide Detector


What the best carbon monoxide detector has

  • A loud alarm. Underwriters Laboratories (UL)-listed devices have a minimum 85-decibel horn that can be heard within 10 feet. Some alarms vary in frequencies to accommodate those with age-related (or other) hearing loss.
  • Interconnectivity. Interconnected alarms are helpful in large homes because they communicate with one another; when one alarm detects a hazard, it triggers them all to sound an alarm. CO alarms can be on the same network as smoke alarms, though all units usually must be made by the same manufacturer. Interconnections are traditionally made via hardwire connections, though many alarms now use radio communications, making for easier installation by a homeowner.
  • Voice alert. Some higher-end alarms include a voice alert. Dual smoke and CO detectors will announce the nature of the hazard, helpful in reducing confusion in an emergency. Some interconnected systems will announce the location of the detected problem on every alarm in the network.
  • Five-year sensor lifespan. The sensors on carbon monoxide detectors will wear away over time. Expect your unit to last at least five years. The better models have an end-of-life timer to alert you when the unit needs to be replaced.
  • Digital display. A digital display can provide a constant readout of measured CO levels, peak levels measured over a period, battery condition and more. On the down side, some might find a lit display a distraction in some situations, such as in a bedroom at night.
  • Testing functionality. CO detectors should be tested once a month. Virtually all detectors have a test/silence button to test the device and also silence the unit in the event of a false alarm. Some alarms had convenience features to silence the alarm with the wave of a hand or a standard IR remote control (like the one used for your TV), but those have proved to be problematical and have largely been dropped, and some detectors with those features have been recalled.

Know before you go

Where should you install a CO detector? Anne Marie Helmenstine, Ph.D.,'s chemistry expert, notes that carbon monoxide is lighter than air, so the best place to install a CO detector is high on a wall (at least five feet above the floor) or on the ceiling. The National Fire Protection Association (NFPA) recommends placing CO detectors in a central location outside of sleeping areas, as well as on every level of your home. Dr. Helmenstine notes that if you are only purchasing one CO detector, put it in your bedroom and "make certain the alarm is loud enough to wake you up." On the other side of the coin, you shouldn't place CO detectors near appliances that produce open flames, such as a kitchen stove, or next to a fireplace.

Battery-powered or hardwired? 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.

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 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.

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, including combination smoke and CO detectors -- and which ones are best for certain situations -- in our smoke detectors report.