Filter construction resistant to the passage of water soluble materials and filtration method

A filter system for filtering the intake air in a gas turbine, the filter system comprising: a) an air cleaner (20¿) first phase; b) an arrangement (60) of filter second stage located downstream relative to the air cleaner first phase and separated therefrom by a space through which air flows, characterized in that the filter arrangement of the second phase, which includes a hydrophobic means (74) includes a microporous membrane having a pore size sufficiently small to inhibit passage of moisture and salt therethrough.