This study deals with behaviour and washing efficiency of a venturi scrubber in self-priming operation. Usually the washing liquid is injected into the throat by means of a pump, in such a way that the amount of liquid added per cubic metre of gas is adjustable independent from the gas flow rate. In contrast to this kind of design, the venturi scrubber used works via a self-priming operation, i.e. the washing liquid is injected by means of a pressure difference between the inside and outside of the venturi throat as a result of the hydrostatic pressure of the liquid and the static pressure of the flowing gas. As is well known from the literature, the cleaning efficiency of a venturi scrubber improves with the amount of liquid added per volume of gas and with increasing gas velocity in the throat. However, high gas velocities and high charges of washing liquid cause a large pressure drop. Hence, the separation efficiency and energy consumption of the scrubber have to be optimized. It is shown that the separation efficiency could be improved by a multistage injection of the washing liquid. Due to the self-priming operation, the separation efficiency remains at a high level even if the gas velocity decreases, and thus requires no regulation from the outside. Liquid separation after the venturi scrubber is realized by an immersion tube in combination with swirl promoters in the diffuser section of the scrubber which increase the rotation of the gas-liquid flow. Thereby, droplets are pushed aside to the diffuser walls and are deposited.