Turn the choke knob on the back of your gas leaf blower so that it turns half way, and then release the screws from the filter cover located on the side of the leaf blower.
Use a rag to wipe off any loose dirt that appears around the filter. Pull the filter unit, and then remove the pre-filter from the unit.
Wash the pre-filter in warm soapy water and then place the filter on a paper towel. Allow for at least one hour for the pre-filter to dry.
Remove and replace the felt filter element if it is dirty with a new felt element, which you can purchase at your local home and garden store.
Slide the pre-filter of the new element on the filter unit and then place back onto the machine. Place the filter cover back on and then tighten the screws.