Filter cleaning/replacing – You need to periodically clean your rangehood. The thin, mesh screen is the grease filter (there may be more than one). It traps airborne oils and grease to keep them out of the motor and vent. To clean the filter, remove it and soak it in a detergent solution until the grease is dissolved. Next, wash it with warm, clean water to remove any traces of the detergent and air dry before re-installing.