Unless you have an AVL Air Shuttle or other pneumatic accessory, you will have only one filter on your loom, and then only if you have a Compu-Dobby. This is the fan filter and it performs two functions: it cools the unit and it removes dust from the air before it is drawn into the fan.a) Compu-Dobbies IThe filter is easily overlooked on our early generation Compu-Dobbies because it is hard to access. The filter on older units is located on the back of the unit, below the solenoids. This means you must remove the CD to clean it. If the filter becomes clogged, it will restrict air flow, heat will build-up in the box, and sensitive electronic components may fail and will need to be replaced. If you do not feel comfortable doing this, we recommend that you remove the filter altogether. It's better to operate with no filter, than with a clogged filter.b) Compu-Dobbies IIIn our Compu-Dobby II design, we corrected the access problem.The filter here is extremely easy to find: it sits atop the solenoid box.In either case, remove the snap-on plastic cover that fits over the fan vent. Remove, rinse, and dry the foam filament. Replace. It is imperative that you clean this filter regularly. We recommend every two weeks, depending on how much you use the loom and what type of yarn you use.