If you put on a dirty filter, the machine does a test, then starts cleaning. After about two hours, the machine itself stops cleaning, dries the filter, and re-runs the test. If the filter is clean, the machine prints a report and shuts down. If the filter is still dirty, the machine starts a second cleaning cycle. If, after a repeated cleaning cycle, the filter remains dirty (or it cannot be washed due to the destruction of the filter itself), the machine prints a report that the filter cannot be washed and turns off.