If your home uses natural gas, or if you have a wood or gas fireplace, you need a carbon monoxide detector. In fact, even if you have an all-electric home, you might consider getting a detector if you use a backup general or other carbon-fueled heat/power source. Inhaling too much carbon monoxide (CO) gas can lead to poisoning and possibly death, so there's pretty good reason to spend $35 on a carbon monoxide detector. In many municipalities, they are required in rental units and/or in newly constructed homes.

Three are three main types of CO detectors: plug-in models plug directly into an existing outlet with battery backup; you can also find models that only use battery power. Lastly, you might see hardwired detectors in newly constructed homes. Most owners of existing homes will opt for plug-in or battery units, that are easier to install.

If you have a large home, you might consider interconnecting CO detectors. Most hardwired systems are interconnecting; when one alarm picks up dangerous levels of CO, all the alarms sound. We did find one model, the First Alert Onelink, that's battery powered but that can also connect to other models to perform this function. That's a benefit in big homes or homes with several floors, where you might not hear an alarm sounding in a distant part of the house.

Lastly, some models combine a carbon monoxide detector with a smoke alarm. While that's one way to cut down on the number of sensor gadgets in your home, these models typically include just one of the two types of smoke-detector sensors (experts say your home needs both types for the best protection).

Consider these tips when shopping for a carbon monoxide detector:

  • Look for the UL symbol on the packaging. UL-listed CO detectors meet product safety standards set by the Underwriters Laboratory, an independent product safety certification organization. These CO detectors sound an audible alarm for CO levels of 150 parts per million (ppm) that remain for at least 10 minutes or CO levels that remain at 70 ppm for one hour. All UL-listed carbon monoxide alarms must also have a manual silence button and sound another alarm within six minutes when elevated levels of CO are still present.
  • Get a detector with a digital display. The display can alert occupants to rising CO levels even before they trigger the alarm. A CO concentration of only 30 ppm may harm heart patients, unborn babies and children, but most detectors don't trigger an alarm until CO levels are 70 ppm or higher. A display indicating no CO is present is also useful for determining whether a triggered detector is merely malfunctioning.
  • A strobe light warns the hearing impaired. Some detectors include a strobe light (or a strobe light can be bought separately and attached) so that someone who is hearing impaired knows an alarm has been triggered.
  • Purchase at least one CO detector for each level of the home. Also install a CO detector in the basement if a furnace or other fuel-burning appliance is housed there.
  • Ideal placement is about head-height on a wall. That's because appliances that produce carbon monoxide usually also produce heat -- so CO rises with hot air in a room. Place CO detectors at the recommended distance from steam sources (e.g., bathrooms and dishwashers), household chemicals and other factors that can trigger false alarms. Position CO detectors 20 feet from all fuel-burning appliances because they emit some CO when initially turned on. Installed CO detectors shouldn't be near windows or ceiling fans, where ventilation might prevent them from sounding an alarm.
  • Regularly check that the CO detector is working properly. If your detector is hardwired directly into your home's electrical system, you should test the unit monthly. For battery-operated units, test the detector weekly and strive to replace its battery at least once a year. You should totally replace detectors every five years unless directed differently by the manufacturer.
  • Consider a test kit. Detectors have a button that test alarms, but they can't mimic CO to verify the sensors are working. Detectagas (*Est. $22) is an example of a kit that can be purchased to test these sensors. It comes with an aerosol can of CO and a plastic bag that seals around the detector and allows you to accurately test that the alarm sounds when a dangerous level of CO is present.
  • Do not connect plug-in units to an electrical outlet that is controlled by a light switch. If the switch is turned off, the detector will begin draining the backup batteries. This leads to frustrating low-battery alerts and requires replacing batteries more frequently.

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