The exhaust air passes over the canopy baffles at high speed. The position of the baffles ensures the grease is thrown out of the air stream by centrifugal force. A fresh water mist is sprayed into the internal plenum of the canopy under controlled conditions which dictate the correct amount of water to ensure the system and airstream is cleaned. The separated grease with water runs into internal collection channels and then to the drainage system. This makes sure that any necessary maintenance is kept to a minimum at minimal cost whilst at the same time providing high levels of hygiene by preventing the build-up of grease which would otherwise create a re hazard.