The four filters in your C4 Cyclonic Canister vacuum should be cleaned regularly for top performance.
First, remove the dirt tank and empty it. With the dirt tank open, twist to remove the dirt cup. The outer portion of the filter can be wiped down. Back at the top of the dirt tank, push the filter button so that the top swings up, revealing the pre-motor filter.
There is a secondary pre-motor filter on the front of the machine, under where the dirt tank latches on.
The post-motor filter is located on the bottom of the machine. Pinch the two tabs to take off the access plate, then push the button at the top to remove the filter.
All of these filters can be washed individually with warm water. Make sure the filters are completely dry and put back in the machine before using the vacuum.