Abstract: An inner tank 6 is arranged on a partition plate 2 in a main tank 1, and a spray nozzle 8 is provided in a top wall of the inner tank 6. A mist separator 33 is formed by a helical tube wound around an outer wall of the inner tank 6. An upper port 33a of the mist separator 33 is connected to a connector block 32 provided at an upper portion of the inner tank 6 and a lower port 33b is positioned at a lower portion of a main mist chamber 5. Smaller particles in a primary mist produced by the spray nozzle 8 float in an upper portion of an inner mist chamber 7. Larger particles in the primary mist descend toward a lower portion of the inner mist chamber 7, and these particles adhere onto an inner wall of the inner tank 6 to form a secondary mist consisting of the smaller particles.