The dusty air extracted containing the waste particles generated in production, is conveyed into a pre-chamber which promotes particle settling. The heavier particles fall into a hopper and are discharged by one or more motorised augers, whereas the air containing lightweight dust particles is filtered by the sleeves and expelled into the atmosphere. The sleeves are cleaned by a system which consists of jets of compressed air controlled by an electronic economiser that optimises jet times and intervals through a pressure differential sensor: the compressed air tank is supplied with the valves already wired.