Vacuum method – Hood test
The Hood Test is an overall leak test. The evacuated test object is covered with a (plastic) hood. The space between the test object and the hood is filled with Helium from the search gas reservoir so the total outer surface of the test object is exposed to the Helium search gas. The helium enters through all leaks present at the evacuated test object and thus the detector connected to it. The detector now indicates the total leak rate. The hood test can for example be used for examination of small vessels.