I have a house with open blinds in Hawaii. The trade winds always bring dust from outside. The Queen of Filters keeps carpets and hardwood floors looking their best. When I change the filters, it is noticeable that the filters prevent dust from escaping. The engine runs for years without any sign of maintenance, so the engine filter has to do its job too. Incidentally, these cones filter out 95% of airborne particles, so they work like cloth face mask filters. All you have to do is create a template and cut out the shape you want. I usually get 6+ face mask filters from each cone (depending on the face mask size).