In general, filters in your vacuum cleaner fall into the realm of mechanical filters. This means that the filter physically traps particles in the filter materials. This trapping makes them very good at removing larger allergens from the air. This includes things like animal dander, dust, mold, and pollen. As long as the air is blowing them around, mechanical filters can remove them from the air. Better filters remove smaller particles from the air, with the best filters able to remove particles that are as small as 0.3 picometers in diameter.