Abstract: A spray booth is disclosed for applying powder coating to substrates. There is a self contained recovery/filter system located beneath the floor of the booth, which recovery/filter system is removably attached to the booth so that another recovery/filter system may be conveniently substituted when changing spray powders, or to facilitate cleaning or repair of the recovery system. The recovery/filter system is so constructed that there are no restrictions in the air flow passages between the booth and the recovery/filter system, with the result that there are no confined areas wherein fires may cause explosions. Powder is collected in the hoppers located in the bottom of the recovery/filter system. The hoppers are generally funnel shaped and are open at the bottom to air transfer pumps which recycle the powder back to the spray system. Vibrators mounted upon the hoppers periodically vibrate the hopper walls to prevent powder from collecting on the walls.