Abstract: A classifier for particulate material of the type wherein a stream of the particles to be classified is introduced into a moving stream of air, classification being achieved by the varying degree of entrainment of the particles in the air stream due to their difference in size. The classifier employs a closed housing having a plurality of outlets, each for a different size of particle, and an inlet located thereabove. An air impeller drives a current of air across the particle outlets. The housing is closed so that the air defining the stream is continuously recirculated. At a point in the air stream downstream of the outlets there is provided an enlarged chamber through which the air flows at an extremely low velocity to preclude particles from being entrained in the air to be carried back to the air impeller.