Filtration soiling-- also called filtration staining-- happens when air is forced into a room faster than it can be removed by the ventilation system. The trapped air has to find a way out and typically ends up being pushed through gaps between the carpet and wall trim or under closed doors. Essentially, this turns your carpet into an air filter because the dust, dirt, pet hair, candle smoke, and other airborne contaminants end up trapped in your carpet. Over time, this darkens the edges of your carpets along the edges of your rooms. All Aces Carpet Cleaning has a special technique for cleaning this type of difficult carpet stain. We can eliminate years of buildup and can save you from having to replace your carpets!