Where there is sufficient false ceiling void space and flexibility is important then ducted units can be used. With the unit concealed completely above the ceiling, air is re-circulated to the room through sheet metal ducting connected to ceiling grilles or diffusers.
Units can also be mounted behind false walls or under floors. This type of system is very flexible as outlet grilles can be moved reasonably easily to suit new room layouts.
Systems can also be tailor made with addition of items such as sound attenuators and extra filtration. Fresh air can easily be introduced into a ducted system.