The National Fire Protection Association (NFPA) recommends replacing smoke detectors every 10 years, including those with 10-year sealed batteries and hard-wired alarms. This is because smoke detector sensors wear out over time, and studies have found that failure rates increase with age. For example, one study found that after 10 years, about 30% of smoke alarms were inoperable.
What does it mean when your smoke detector is yellow?
If your smoke detector has turned yellow or a yellowish brown, it's not dirty – that's by design and means it's time to replace it
Smoke detectors start as white but will develop a yellowish color over time. The discoloration is due to bromine, which helps the equipment withstand flames and blare its alarm. It takes years for bromine to turn a smoke detector yellow, so you can use color to know when to replace the device.