This is a common carpet stain, called filter lines, that we run into while cleaning carpets in Tampa FL. In previous articles I have mentioned how your carpet is like a giant filter in your home. It removes fine particulate matter from the air and holds it until it is removed by vacuuming or a professional carpet cleaning. Filter lines are just a line of soil in the carpet where air has past through the carpet and deposited soils and other fine material until it builds up into a visible stain. They often show up at the base of a wall or under a door that is kept closed. In this case the home owner was an avid smoker who kept the door to the guest room closed most of the time. The smoke particles would be carried through the air and under the closed door where the carpet would filter them out. Chem-Dry's carpet stain remover, called Filter Line Remover, was used to remove this filter line stain in the carpet.
I'm sure I could do a PSA about what smoking does to your lungs with this photo, but it's important to point out what carpet can do for the air quality in your home and what our carpet stain remover can do for your carpet. At Chem-Dry of Tampa FL we have several carpet stain removers formulated for different types of stains. The good news is that if we can't get it out no one can.