Maybe you already have a full collection of smoke detectors and carbon monoxide alarms and change their batteries diligently every year. Even so, each of these devices has a limited life: Five years for CO alarms and combination CO/smoke detectors, 10 years for stand-alone smoke detectors. You’ll find the manufacture date on the back of the alarm. And replacing them isn’t that big a deal: My husband and I changed both recently (full disclosure, my hubby did most of the work).

If you don’t already have these critical home safety alarms, take heart: A top-scoring Kidde smoke alarm in Consumer Reports’ tests costs only $23, while a top First Alert CO detector will set you back just $40. Not all alarms are the same, however. Some CO alarms took twice as long to sound as others in our tests (Ratings are available to subscribers). But any CO alarm is better than none at all.

And when it comes to smoke alarms, we recommend dual-sensor models—those that utilize both an ionization and photoelectric smoke sensor like the Kidde because they’re good at detecting both smoldering and fast-flaming fires.

Unless you live in a small apartment or one-level home, you’ll need several alarms around your home. Battery-only alarms and plug-in CO alarms are easy do-it-yourself projects. Look for smoke alarms with hush buttons, so you won’t be tempted to disable your detector during a false alarm. And when you install the new alarms, put the date on them, either with a marker or tape. That way you’ll know at a glance when they need to be replaced again. (We recommend checking them in the fall and late winter when you reset your clocks.)

—Celia Kuperszmid Lehrman