Diagnosis
The reusable pre-filter is located behind the front grille. It captures large particles and needs vacuuming.
How to Fix It
Power off and unplug the unit. Remove the front cover by pulling from the bottom. The black mesh pre-filter is attached to the back of the cover. Use the brush attachment on a vacuum cleaner. Gently vacuum all surfaces of the mesh. Do not wash it with water. Reattach the cover.
If That Didn't Work
If the mesh is damaged or cannot be cleaned sufficiently, Molekule sells a replacement pre-filter. It is a separate part from the main PECO-Filter.
Heads Up
Never rinse the pre-filter. Water will trap particles in the mesh and can promote mold growth inside the unit when reinstalled.