Use FreeNotification to register AComponent as a component that should be notified when the component is about to be destroyed. It is only necessary to register components this way when they are in a different form or have a different owner. For example, if AComponent is in another form and uses the component to implement a property, it must call FreeNotification so that its Notification method is called when the component is destroyed. 

For components with the same owner, the Notification method is called automatically when an application explicitly frees the component. This notification is not sent out when components are freed implicitly, because the Owner is already being freed. 

Notification 

RemoveFreeNotification 

Owner