First Alert SA340CN

Reviews say the First Alert SA340CN (Est. $20) is a good pick for people who don't like to change batteries. Although some owners say the lithium battery, which is supposed to have a 10-year lifespan, lasted far less than a decade, the National Fire Protection Association Journal suggests any such failure is more of a consumer issue than a safety problem because the First Alert SA340CN chirps to indicate that the battery is low. Even so, the battery isn't user-replaceable, and you do have to buy a new unit eventually. It's important to note that the First Alert SA340CN is best at sensing fast-flaming fires and not as adept at detecting slowly smoldering blazes. For a detector that can sense both types of fires, you need a dual-mode model like the First Alert SA302CN (*Est. $25).

We found the best reviews at ConsumerGuide.com, which gives the First Alert SA340CN a rating of "excellent" for performance but doesn't explain its testing methods. A few other owner reviews are available online; those at Amazon.com provide a balanced mix of plusses and minuses, the latter mostly related to battery performance. A report in the National Fire Protection Association Journal is not a product review but rather an analysis of 10-year batteries in smoke detectors.