The dark marks on carpet and rugs are caused by what is known as filtration soiling. Filtration soiling is most commonly found around baseboards, under doors, along the edges of stairs and most commonly near HVAC vents. Such soiling can be the result of fireplace emissions, neglecting to change air filters, and can even come from cooking oils that have become airborne and settled into the carpet. Very challenging to remove, filtration soiling often develops over a period of months or even years; however, it can also develop fairly quickly. Let’s go over a few steps for removing filtration soiling.
Scrape away surface fibers by running a hard-bristle scrub brush over the surface of the discolored part of the carpet. For this technique to be effective, it’s important to do it before you get the carpet wet.
Install the crevice tool on the end of your vacuum cleaner hose and vacuum the area you just scraped. You should see a noticeable improvement after you’ve scraped and vacuumed, but some of the discoloration will probably remain due to greases, oils and electrostatically bound particles. You will need to wash this away.
Moisten a white rag with clean hot water and rub the carpet vigorously. It’s important to use a white rag to avoid transferring any dyes to the carpet. If the carpet is sufficiently clean after wiping, your job is done. If not, please proceed to step 4.
Mix a solution by adding a cup of white vinegar to a gallon of warm water. A solution of equal parts of water and hydrogen peroxide is also an effective cleaner. Test your solution on an inconspicuous part of the carpet to make sure it won’t affect the color or damage the baseboards. Work the cleaning solution into the carpet with a scrub brush. It’s important to agitate the carpet fibers to loosen the dirt particles so you can remove them.
Spray clean water on the carpet, scrub lightly, then wipe or blot as much water off as possible. Let the carpet dry, then vacuum again to remove any surface dirt and loose fibers that remain.
Filtration soiling is a relatively common problem but you can minimize it by cleaning your furnace air filters regularly or replacing them when they are dirty. Follow these steps if you notice those little black lines around your baseboards, under doors, edges of stairs or near HVAC vents. Cleaning the affected areas will also remove those harder to get to pollutants.