Abstract: The filter is formed by a wall (6) separating a vacuum chamber (3a, 3b) from a space (1) where a paint spray gun (2) is located. The lower part (5) of the wall (6) dips into the water of a collecting tank (7). The wall (6) is pierced by a multiplicity of holes, in each of which is fastened a tube (8) projecting on its two faces. On the same side as the vacuum chamber (3a, 3b), each tube is equipped with a deflector (10) at its outflow. Water from a reservoir (11) flows off via an overflow (12) and streams (15) over the entire upstream face of the wall (6). This water rebounds on the projecting parts of the tubes (8), and the shape and size of the pent roofs (9) guarantee that the tubes (8) suck up the best possible mixture of air and water. This assists the capture of paint droplets by the water. The deflectors, by compelling the mixture of air and water laden with paint droplets or other impurities to change direction abruptly, assist the capture of these droplets by the water.