The purpose of this document is threefold: (1) to review the issues associated with moisture in avionics equipment, (2) to outline methods for correcting conditions of excess moisture in existing avionics installations, and (3) to recommend design practices for new avionics cooling system installations which will minimize the occurences of excess moisture in avionics.

This document does not address all moisture-related requirements which may be applicable to the avionics installation. For instance, when the air conditioning system is inoperative when the aircraft is parted or stored, or if an avionics ground cooling fan is employed, the aircraft and its equipment will be exposed to and must withstand the effects of the outdoor environment (e.g., high humidity, fog, rain, and surface condensation).