There are a lot of circumstances in which you should consider before using an AED!
1.If a person had excessive chest hair, you will need to remove the hair before placing the AED pads on a persons chest.
2. Some people have medicine patches, if a medicine patch is located near/on the chest area the you will have to remove them.
3. If a person is covered in water and/or sweat, attempt at removing all liquid substances.
Those are just a few, but i hope this helps! Remeber to stay safe!