How do you change the battery in a smoke detector?

Smoke alarm batteries are easy to replace, once you find where they go. The design varies from brand to brand.

Usually, the battery is located on the side of the alarm, either in a "drawer" or a swinging compartment. There may be a small plastic latch holding it closed. Occasionally, it is necessary to remove the alarm from the wall or ceiling to find the battery compartment. This can be done by rotating the entire alarm counter-clockwise until it releases. The battery compartment is designed not to close if the battery is inserted incorrectly.

Many smoke alarms have an option to permanently screw the battery compartment closed. This is typically done in rental units to prevent tenants from removing the battery during a false alarm. In this case, the landlord is required by law to change the battery. If you are the landlord, consult the alarm documentation (which can be found online) for instructions on how to remove the locking screw.