An apparatus for air treatment includes at least one reservoir which can be filled with a liquid, an air-conveying device and a device which ensures that for the treatment of the air to be treated the air comes into contact with at least a part of the liquid. A circulating device is provided, by which liquid in the reservoir is conveyed in a circuit out of the reservoir and back into the latter. For the purpose of sterilising the liquid, a device for mechanico-physical opening of cell membranes, for instance by electroporation or cavitation, is provided in the circuit. Such an apparatus can also be used for purifying exhaust air in a surface treatment installation.