Automated External Defibrillators (AED) are battery powered and should include some basic medical supplies. The batteries need to be replaced as deemed by the manufacturer but should be verified monthly to verify the battery status. Most units have an external indicator that shows whether the unit is ready for use or needs attention.
The defibrillation pads used to connect the AED to the person also expire periodically and should be checked. The best practice is to visually inspect the AEDs monthly to ensure that they have not been tampered with, are accessible, and ready for use. The batteries, defibrillation pads, and any accompanying medical supplies should be replaced before their expiration dates.