You see it all the time. An otherwise good looking carpet that turns dark and discolored right where the wall meets the floor. It’s especially noticeable on lighter colored carpets, and chances are, it is an older home. This darkening is referred to as Filtration Soiling sometimes called Edge Filtration Soiling. It is caused by very fine microscopic particles flowing under your carpets and up through the gaps along the wall, air vents or under doors. The carpet catches these particles and traps them like a filter. While it’s more likely to happen in an older home, we’ve seen it show up relatively quickly in newer homes as well. On a comforting note, at least it’s not due to some hidden issues behind the walls. A good cleaning will take care of it at least for a while, but it’s generally nothing to be overly concerned about aside from the appearance.