a louver assembly , which acts as a water - removing inertial separator , is located in the air intake of an enclosure maintained at negative pressure . the louver includes a number of spaced vanes , each formed without discontinuities by simple bending into a stair - step - like configuration when viewed end - on . air enters the enclosure by passing between adjacent vanes , experiencing changes of direction of between 70 degrees and 90 degrees at the vane &# 39 ; s surfaces to separate water therefrom .