An apparatus for coating or encapsulating articles , comprising a drum with a perforated wall rotatably mounted in a wrap-around chamber , the drum being suitable for containing and removing a batch of articles to be coated during the rotation of the drum; a dispenser group with at least one nozzle for spraying a coating product on the articles contained in the drum; at least one gas inlet to the chamber on a first side of the drum to direct clean drying gas against the perforated wall of the drum and at least one gas outlet from the chamber to the other side of the drum, adjacent to the perforated wall of the drum to extract from the chamber dirty drying gas that has passed through the drum, the apparatus being characterised in that it comprises - an adjustable closure system , interposed between the drum and the gas outlet of the chamber , capable of defining an effective passage for the dirty drying gas smaller than the passage offered by the gas outlet of the chamber and further displaced or concentrated coinciding with an area of the perforated wall of the drum that is effectively covered by the batch of articles ; - a controller , which operates the said closure system for at least automatically adjusting the status thereof or triggering a recommendation signal , if the status of the closure system is not optimal or is not in concordance with the area of the perforated wall of the drum that is effectively covered by the batch of articles ; and - a drying gas suction group , downstream of the chamber , capable of providing vacuum conditions in the chamber and consequently promoting a flow of dirty drying gas in one outlet direction (L) of the chamber; wherein the closure system has several gates placed across the passage of gas, superimposed and configured in the form of blades which, like a slatted shutter, are rotatably assembled around respective rotation axes essentially normal to the direction (L), with more than one gate being actuatable between at least one open position (A), wherein the blade is arranged essentially parallel to the direction (L), and a closed position (B), wherein the blade is essentially normal to the direction (L), so that a cascade arrangement of the gates from the open position (A) thereof to the closed position (B) thereof, starting with the one at the highest level and continuing with the one immediately below, causes a gradual reduction in the passage of gas and the concentration thereof towards lower positions of the perforated wall of the drum . - an adjustable closure system , interposed between the drum and the gas outlet of the chamber , capable of defining an effective passage for the dirty drying gas smaller than the passage offered by the gas outlet of the chamber and further displaced or concentrated coinciding with an area of the perforated wall of the drum that is effectively covered by the batch of articles ; - a controller , which operates the said closure system for at least automatically adjusting the status thereof or triggering a recommendation signal , if the status of the closure system is not optimal or is not in concordance with the area of the perforated wall of the drum that is effectively covered by the batch of articles ; and - a drying gas suction group , downstream of the chamber , capable of providing vacuum conditions in the chamber and consequently promoting a flow of dirty drying gas in one outlet direction (L) of the chamber; <EOS>