In most cases, after the air is warmed or cooled at the source, it is distributed to across rooms with different ways like forced-air, gravity, or radiant systems. These systems have their own way of functioning. Forced air method uses blower (a powered fan) that forcefully pushes the air through ducts. Gravity method is used only in heating systems as where air is warmed; it rises above the cool air, ready to be distributed through outlets. And finally the radiating systems use electric heating panels to generate heat, which is radiated into rooms.