An experimental investigation was conducted to study the flash boiling process and the influence of the exiting restriction (orifice) size on the mass flow during flash boiling of HCFC-22 in a glass pressure vessel. An apparatus was built and a combination of tests were run with three interchangeable exiting orifices (1.59, 3.18, and 5.56 mm diameters). The flashed vapor was vented from a 1110-mL vessel to a large ＇＇semi-infinite＇＇ tank initially set at 120 kPa. Calculations revealed that the refrigerant flow exiting the vessel was choked, depending on the orifice size. Smaller orifices were choked longer, had slower depressurization rates, and reduced mass flow rates. The depressurization rates were greater for tests using larger orifices which enabled the liquid to become more highly superheated, up to 41 degrees C for one test case, and ultimately vaporize more refrigerant.