Q&A: When should I replace a carbon-monoxide alarm?

I've heard that carbon-monoxide alarms fail after seven years. Is that true?

Most carbon-monoxide (CO) alarms are backed by a five- to seven-year warranty, but they typically emit a chirping or signal when they're nearing the end of their useful life. This signal differs from the one that indicates a low battery. If there's a problem with the unit, a model with a digital display will show an error message, and one without a digital display might flash LEDs in a particular pattern.

Remember, the test button on a CO alarm checks only whether the alarm is working, not the sensor. To check the sensor, use a test kit that you can purchase at a local home center.

Essential information: Read our buyer's guide to CO and smoke alarms for more information on these important safety devices, and view a quick interactive to determine which alarms are best for your home. We've also got a report on an intriguing study on the effectiveness of a voice recordings versus more traditional loud tone alarms in awakening children.