Precision cleaning of parts is performed with liquefiable gases, such as CO.sub.2, without the use of a complex and costly processor system. Rather, simplified and reliable performance for small scale and "low end" cleaning applications is accomplished without the use of pumps and condensers. The apparatus for removing undesired material from a chosen substrate comprises: (a) an enclosed cleaning chamber in a walled vessel for containing a liquid derived from a liquefiable gas and the substrate containing the undesired particulates and contaminants, the walled vessel adapted to withstand a maximum pressure of about 1,500 pounds per square inch (105.4 kg/cm.sup.2) at ambient temperature; (b) means for supporting the substrate in the cleaning chamber; (c) ultrasonic energy-producing transducer means attached to the walled vessel within the cleaning chamber; (d) inlet means attached to the walled vessel for introducing the liquefiable gas into the cleaning chamber under a pressure less than about 900 pounds per square inch (63.3 kg/cm.sup.2); (e) temperature control means connected to the cleaning chamber for controlling the temperature within the chamber up to about 50.degree. C.; (f) reservoir means for providing the liquefiable gas to the inlet means; (g) means for changing the liquefiable gas to the liquid; and (h) outlet means in the chamber for removing the liquid from the cleaning chamber. The liquid may then be further treated to remove particulates and organic contaminants and either recycled to the cleaning chamber or vented to the atmosphere. The process is especially applicable for general degreasing and particulate removal processes, when high precision cleaning is not required.