Most smoke detectors last only 10 years and contain radioactive Americium 241, so send dead ones back to the manufacturers like these:
Send First Alert, BRK and Family Guard Smoke Detectors to: BRK Brands, 25 Spur Drive, El Paso, TX 79906, (800) 323-9005. On the front of the package, write “For Disposal.” Up to 5 smoke alarms are accepted for free.
AMERICAN SENSORS AND DICON
Ship American Sensors and Dicon Smoke Detectors by surface mail to: Dicon Inc., 20 Steelcase Road West, Unit #3, Markham, Ontario L3R 1B2, Canada, (800) 387-4219. On the front of the package, write “For Recycling, $0 Value.”