Fuente: WIPO "rice" An air conveyor comprises a generally flat deck divided into a plurality of zones (5A-5D). The deck in each zone is provided with parallel rows of slots for the passage of air from below. The slots are arranged to generate a generally linear air flow across each zone of the deck. The space beneath the deck is divided into a plurality of separate plenum chambers and air is controlledly supplied to each of the plenum chambers.