4.4 Spraying deviceThe device for s

4.4 Spraying deviceThe device for spraying the salt solution comprises a supply of clean air, of controlled pressure and humidity, a reservoir to contain the solution to be sprayed, and one or more atomizers.The compressed air supplied to the atomizers shall be passed through a filter to remove all traces of oil or solid matter, and the atomizing pressure shall be at an overpressure of 70 kPa1) to 170 kPa. The pressure should be 98 kPa ± 10 kPa.NOTE Atomizing nozzles can have a “critical pressure” at which an abnormal increase in the corrosiveness of the salt spray occurs. If the “critical pressure” of a nozzle has not been established with certainty, control of fluctuations in the air pressure within ±0,7 kPa, by installation of a suitable pressure regulator valve, minimizes the possibility that the nozzle will be operated at its “critical pressure”.In order to prevent the evaporation of water from the sprayed droplets, the air shall be humidified before entering the atomizer by passing through a saturation tower containing hot distilled water or deionized water at a temperature 10 °C above that of the cabinet. The appropriate temperature depends on the pressure used and on the type of atomizer nozzle and shall be adjusted so that the rate of collection of spray in the cabinet and the concentration of the collected spray are kept within the specified limits (see 8.3). In Table 1, guiding values are given for the hot-water temperature in the saturation tower at different pressures. The level of the water shall be maintained automatically to ensure adequate humidification.