It has a very strong suction, which is important to clean the pot (no need to scrape with a spatula soot that is attached to the crucible and other parts of the heating fireplace). Small flat, like soot is relatively thin, the filter becomes clogged and the suction is not as strong. It should remove and clean the filter time to time, which is relatively easy to achieve. I advise to clean it, if possible, with the blow of an air compressor, otherwise just shake it to unclog.