These dark lines are associated with air pollution from air flow, and may permanently alter the appearance of your carpet.
If So you are experiencing what is called Filter Soiling Or Soil Filtration.
This happens when air pressure and currents encounter a restriction, the air will pass through the carpet. The carpet acts as a filter trapping whatever small particulates, oils and other pollutants are in the air. Filtration soiling is most easily observed on white or light colored carpet but it can occur on any color or fiber.
Filtration soil may include candle soot, particles from incomplete combustion due to a furnace puff back or misadjusted furnace, cooking oils, vehicle exhaust and particles from a myriad of other sources. These very small particles stick tightly to the carpet fibers. They are difficult to remove with agitation.
However, they can be removed by products that lubricate and suspend the fine particles. Because the exact make-up of filtration soil will vary from job to job, how well the stain responds to cleaning will also vary.
Note: Although most walls appear to be solid there are usually gaps along the bottom of the wall board.
Air passes through these gaps carrying soils into the carpet.
For a permanent solution to filtration soiling along
walls follow these steps.
1. Disengage the carpet.
2. Caulk the edge where the wall meets the floor.
3. Rest retch and trim the carpet. This will usually
remove present filtration soiling.
4. Double tuck the carpet back into the gulley
between the wall and the tack strip
CAUTION: When you encounter filtration soiling there is a
possibility that it is accompanied by fume fading. Fume fading
refers to color loss as the result of gases passing through the
carpet.
Fume fading is often hidden by filtration soiling and not noticed
until the filtration soiling has been removed. It can then
appear that the cleaner caused the color loss. It is wise to
check for fume fading and inform the consumer if it found. Do
so before it becomes an issue.
How do you remove filtration soil?
Filtration soil is difficult to remove and if it is very dark, the most you can generally hope for is an improvement in appearance. When dealing with this dark, oily discoloration’s you are challenged with a blend of many pollutants, of varying particle sizes.
Cleaning of filtration marks is not a one step process. The cleaning will require a solvent to attack the oily substance, detergent to attack soil, a lot of agitation, plenty of dwell time for the chemicals to work and a thorough very-hot water extraction. This type of cleaning is not done standing up with a cleaning wand. You will be working face to face with the carpet if you expect any type of cleaning results.