What Are Those Dark Carpet Stains Along My Walls?

Posted by Sams Carpet | October 23, 2018 | Sams News

Have you ever been vacuuming and noticed that there is a dark colored grime around the edges of your carpet? If you notice there are dark lines on your carpets located along the walls, around the air vents, or under the doors, you most likely have what we refer to in the industry as filtration soiling. Many homeowners experience this, and the great news is, there is a way to deal with it.

Filtration Soiling – what is it?

Filtration soiling is caused when air passes through the carpet as it escapes through the gaps between the subflooring or where the baseboard and the carpet meets. The air that passes through these gaps can deposit microscopic particles made up of dust, pollen, ash from a fireplace or even a candle. Any home with an HVAC system is subject to filtration soiling. The grimy buildup is a gradual process and the accumulation will slowly become visible, and the lighter your carpets are the more noticeable the issue will be.

Another culprit is soot from burning candles.  Yes, we know that many people love burning candles, but unfortunately, this practice can come with a consequence as soot from the candles causes filtration soiling.

How to Prevent it?

There are several things that you can do to help prevent the soiling. Make sure that your HVAC system is properly sealed at the connection points. You should also make sure that your house has been properly insulated so that air can flow in and out of your home.  In addition, it is important to change the filters in your HVAC system every 6 months or sooner directed by the manufacturers of the filters. Here are some other tips:


  • Seek higher quality candles. While candles made from soy or beeswax are said to burn cleaner, this isn’t always the case. Look for candles that are made with minimal impurities.
  • Read the instructions for any unique maintenance tips.
  • Get in the habit of trimming wicks to ¼ inch to reduce the release of soot.
  • Make sure your candle burns low and even for a cleaner burn.
  • Use a snuffer to extinguish the flame, which will reduce the emission of black smoke.
  • Open windows regularly to ventilate your home and avoid a mold or soot problem.
  • Choose unscented candles. The fragrance or aromatherapy oils used in scented ones create more soot. Diffusers are more effective when you want to scent your home.


  • Use candles that feel soft and greasy. These tend to burn more smoke.
  • Burn candles near a draft. It might seem counterintuitive, but wind can disturb the flame and consequently create more soot.
  • Place candles in narrow-mouth containers. They restrict the airflow of a burning candle, leading to more soot emissions.
  • Leave candles unattended (though we’re betting your parents taught you that one long ago).

How to Remove the Soil Stains

Once you have noticed the soiling, and ensure that your HVAC system is properly sealed and your filters have been changed, you will need to have both your ducts and carpets professionally cleaned. We would not recommend trying to clean the carpet with a spot cleaner or without professional assistance. The soil is usually greasy and extremely fine in its composition and attempting to clean the stains without professional help will only lead to further carpet damage.

At Sams we offer both professional air duct cleaning and a specialized carpet cleaning procedure to remove all or most of the filtration soiling. As always, prevention is the best medicine, so as soon as you notice the build-up occurring, give Sams a call so that we may provide you with a FREE estimate. We will be sure to do our best to return your carpets to their original beauty.

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