A common, but somewhat strange, carpet complaint is the appearance of dark or black lines in an otherwise clean carpet. What are these lines? What causes them? How can you get rid of them? In today’s blog, we’ll tell you just that.

The source of black lines

The dark lines that can appear in your carpet are likely due to filtration soil. Filtration soil is caused by air pollution in the home- and it sounds a lot more serious than it is! In essence, when air circulates through your home, your carpet acts like a filter. It catches tiny particles inside and traps them, keeping them in the fibers. And the particles that lead to black lines are both tiny and oily, usually the byproducts of something burning. This can be a few things, such as:

  • Candles
  • Fireplaces
  • Furnaces
  • Stoves

The air conditioning or HVAC system in your home moved these particles around and around. At the edge of a carpet, below the surface, there is a tack strip to hold it in place, and here there is no padding. This “gap” allows air to flow through, down the cavities in the walls, and back to the air return. This is normal- homes need to breathe!

What can you do?

Filtration soil, while normal, can be a little difficult to deal with. Only a professional carpet cleaning company with experience dealing with filtration soil specifically will be able to get it out. Normal carpet cleaning processes will still leave the residue behind! Many carpet cleaning companies will simply tell potential customers that the filtration soil marks will never come out and impossible to remove. This isn’t true! However, the best cure is prevention. Here are a few ways you can help keep this from becoming an issue:

  • Choose a dark carpet color, since this is less likely to show coloration
  • Replace furnace filters regularly and keep up with furnace maintenance
  • Keep doors open to allow proper air flow inside
  • Vacuum frequently, making sure to use tools to reach along the edges of your carpet
  • Limit how often you burn candles or use your fireplace
  • Keep large flat items off of your carpet whenever possible
  • Have your carpet cleaned professionally, thoroughly, and regularly


Not every home has issues with filtration soil, and not every home that does has them in every room. But whatever the extent is, it can be very difficult to manage! If you are dealing with dark lines on your carpet that don’t seem to go away, please give us a call at All-Star Chemdry. Our expert team will assess your situation and get you settled as soon as possible!