Abstract: Small, hermetically sealed pans are leak tested after subjecting the finished device to an environment of trace gas such as helium. During the testing process the pans may lose their helium charge by rapid escape due to massive gross leaks. These cases demand pre-helium mass spectrometer leak detector gross leak testing procedure. The non-helium expansion technique, used in conjunction with a helium mass spectrometer leak detector, provides a reliable and automatic gross and fine leak testing of the pans by a single apparatus. The test pan is placed in a sealed test fixture, and a valve between the test fixture and an expansion chamber is opened. The pressure in the expansion chamber is measured after the valve is opened. When the measured pressure is less than a reference pressure, a leaking test pan is indicated. When a sealed test pan is indicated, a helium mass spectrometer leak test is performed to determine the presence of fine leaks in the test part.