Abstract: The method for separating particles having mixed density and/or size, comprises dispersing the particles in a fluid stream, passing the fluid stream into a housing which causes the fluid stream to be diverted from its original direction, and capturing certain of the particles within the housing which deflect the least amount in response to the directional diversion of the fluid stream. Apparatus for accomplishing this method include a channel in which the air flow undergoes a change in direction of 90.degree., one boundary being a right angle bend and the other being formed from a circular curve or rectangular hyperbola. Another device for accomplishing the method includes an inlet channel which enlarges in diameter and which includes capturing means placed along the longitudinal axis of the inlet channel, whereby the fluid must divert radially outwardly around the capturing means as it passes from the inlet channel through the enlarged portion thereof.