At the tracer probe test the same set-up as used for the hood test is applied, but without the hood. A spray gun is used to spray a fine jet of helium search gas at areas suspected of leaking. Again the helium enters through leaks present at the evacuated test object and the detector connected to it. The detector indicates if a leak is present at the area the helium search gas is exposed to.

The tracer probe test can for example be used on seals, flange connections, weld seams etc..