A powder coating system is provided comprising a powder spray booth (2) with a powder recovery system having an overspray intake (18) communicating with the interior of the booth. A diverter plate (26) may be held within the booth (2) to define with the booth floor (10), a duct leading to an overspray intake (18) of the powder recovery system. The diverter plate may include apertures for allowing oversprayed powder to be collected through the plate. The diverter plate may be provided as two or more diverter plates held at different elevation levels within the booth to define a duct which is larger in parts of the duct which are closer to the overspray intake than parts of the duct which are farther from the overspray intake. Alternatively or additionally, the coating system may include an air assist which provides jets of air across a portion of the interior surface of the booth. The surface may be one or more sloped portions (22) of the floor. The air supply may be pulsed to produce periodic bursts of air across the interior surface.