With test rigs of series DHP 145 it is possible to test tightness against over and low-pressure of components of different dimensions and shapes. The leak rate is determined depending on pressure. Overpressure is accomplished with compressed air (from the network), the pressure level is adjusted by means of a proportional valve. When operated in the suction mode, the necessary underpressure is created by means of a pneumatically operated vacuum pump. The test rig is working at test air temperatures from -40°C up to 120°C. A heat exchanger protects the measurement instrumentation against damages because of too low or high temperatures during low pressure operation. For external connection the test rig has a test air adapter, a pressure measurement port as well as a temperature sensor which have to be connected with the test sample. All connecting lines are 2 m long so that the sample can be in a climatic chamber during the test. The whole inspection process is carried out primarily automatically and is controlled by means of the PC-based software DHPWin.