Dark, shadowy, dirty lines on the carpet along baseboards, under doors, beneath draperies and along the edges and in the crevices of carpeted stairs are visible signs of an aggravating—downright gross—problem called filtration soiling.

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Filtration soil comes from airborne pollutants passing through the carpet as the air is drawn through the crack between the carpet and the baseboard, around the drapes or under a closed door.

Filtration soil is an accumulation of soot from dirty ducts, smoke from candles and the fireplace; tobacco, kitchen grease from the oven and cooktop; smog, auto emissions and pollutants from outdoors.

A home’s HVAC (heating, ventilation and air conditioning) system is designed to filter out airborne soil, trapping it in the HVAC filter. But once the filter is full, the system will send the air pollutants back into the house through the ducts where all of that icky mess gets lodged into corners and crevices.

Normal vacuuming is no match for removing filtration soil. And neither are the best carpet spot removers. Filtration soil is greasy and sticky. It requires the big guns.

A severe care of filtration soil may require the services of a professional carpet cleaner who specializes in this unique problem. However, it is possible to effectively do it yourself provided your soil problem is not severe.


  • Using the vacuum crevice tool, vigorously vacuum the areas suffering with filtration soil to remove any loose debris and dust from the crevices.
  • Use a specific cleaning product for this kind of soil like Prochem Filter Out, specially formulated to remove filtration soil lines, soot and other electrically-charged particles. (About $17). Apply it undiluted so that it saturates the fibers in the stained areas. Allow to sit for 3 to 5 minutes.
  • Scrub the lines of filtration soil with a good, strong brush that can get down into the crevices.
  • Extract completely using hot water or All Fiber Rinse—not absolutely necessary, but an excellent product that will assure a good, clean rinse. (About $36). Use a wet dry vacuum to do this if you have one available, or blot well with a clean white cloth.
  • Repeat as needed depending on the severity of the problem.


  • Have your air ducts cleaned professionally, ideally once a year.
  • Change the filter(s) on your HVAC system once every three months without fail.
  • Thoroughly clean the filter in the range hood, weekly.
  • Use the range hood fan and vent every time you use the oven or cooktop. You want all of that smoke, cooking oil and airborne residue to leave the house immediately.
  • Keep doors and windows closed if you live on a busy street or in an area with a lot of pollutants.
  • Make your home a smoke-free zone. All smoking should be taken outdoors and away from open windows and doors.
  • As lovely as candles and aromatherapy can be, these can contribute to a filtration soil problem. Switch to flameless LED candles, which create a lovely, realistic ambience. Some even have fragrance.
  • If you use a fireplace make sure the system is clean and the pollutants it creates are being properly removed from the house. Clean the chimney and filter (if any) regularly as well as any filters.
Photo credit: CarpetCleaning.com
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