Rinse the filter shroud off in water. Particulates should come off fairly easy, as they should be small. If not, scrub lightly.

Rinse the foam filter off, working the particulates out with water, being careful not to damage the filter.

Run water through the HEPA filter in the opposite direction of the airflow. The water should be hitting the side that the foam filter usually is mounted on.

Place all three items somewhere to dry.