Abstract: Apparatus and method to inject an air stream with dry ice or other sublimable particles to be blasted against a surface to be cleaned. An air lock assembly (20) with an air stream passage (21) and an intersecting conveyor passage (13) that has an endless cable conveyor assembly (38) passing through it. The conveyor (38) passes through a hopper (30) of dry ice particles before entering the air lock (20) and injecting the air stream with dry ice particles. V-seals packings (18) are provided as a means of limiting air form escaping from the points where the conveyor (38) enters and exits the air lock assembly (20). An adjustable speed motor (10) drives the conveyor (38) thereby giving an adjustable control of the ratio of dry ice to air.