What is the expiration date for these? (i.e. Have they been sitting on a shelf for 5 years?)

I was told by a fire marshal that smoke detectors have to be replaced every 10 years from date they were physically made.

Thank you for your feedback. The date f manufacture is on the back of the unit. However, your detector has a 10-year warranty based on when the device was purchased. If you have any additional questions, please don’t hesitate to reach out to us at First Alert at 1 (800)-323-9005.