Smoke detector batteries should last at least one year under normal conditions.
Residential fire deaths have decreased steadily as the number of homes with smoke detectors has increased. Reports from the National Fire Protection Association on residential fire deaths show that people have nearly a 50 percent better chance of surviving a fire if their home has the recommended number of smoke detectors.
Smoke detectors that are 10 years old are near the end of their service life and should be replaced. A smoke detector monitors the air 24 hours a day. At the end of 10 years, it has gone through over 3.5 million monitoring cycles. After this much use, components may become less reliable. This means that as the detector gets older, the potential of failing to detect a fire increases. Replacing them after 10 years reduces this possibility.