Abstract: A filtering apparatus for reducing problems due to water condensation in mobile or portable electronic instruments through the use of a controlled air path into an otherwise sealed enclosure. The apparatus includes a screen with a fine mesh for condensing water particles contained in the air that flows through the path with the screen positioned so that the condensed water flows out of the enclosure, and a dehydrating material located in series with the screen for absorbing additional moisture from the air. The apparatus is designed to fit almost entirely within the enclosure while being readily accessible for easy replacing of the filtering components.