Like removing all the layers and/or masks?
Areas can just set off monitoring and monitored status or turn off both layer and masks, the current behavior is kind of buggy (they seem to look for layers and masks instead of masks only, and react when not monitoring but are monitored).
Btw, I'm talking about the CollisionObject here (the parent), not the CollisionShape node because it is just a helper that uses the same shape resource as the parent.