Are you seeing dark streaks discoloring the edges of your carpet near the wall? You might also see a similar effect taking place on carpeted stairs (the vertical portion you are not stepping on). This might not be happening in every room, but if it happens anywhere, here is a breakdown of what is happening.
The Cause: Filtration Soil
The pollutants in an average home are numerous. Many of these particles are just moving through the air. And because soil particles are heavier than air, they all end up on the floor. The final step in this process is the soil ending up on the carpeted portion of the floor.
Your carpet acts as a filter for these soils. Just as a coffee filter is a weave of material that catches larger particles, the weave of a fabric floor covering similarly keeps soils from passing through the carpet and falling out of sight.
Where do these soils come from exactly? Most often, they are ash resulting from burning from a fireplace, candle, incense, stove, and furnace. These soils will not just end up next to the flame as the air currents and ventilation pass the soil through the house.
Most of the time, filtration soil ends up along the walls. But placement usually has to do with areas not getting regular cleaning. It is difficult to clean the edges of your carpet along the walls because of the dimensions of a vacuum cleaner, but these soils are often oily and cannot be cleaned with suction alone.
Aesthetic Solution: Darker Carpets
If you are only looking to have these markings look less distracting or attention-grabbing, you can use carpets that are darker in color. The darker your carpet, the less obvious soils are going to be. It is not a great solution, but it solves the problem of optics caused by filtration soils.
You should still call to clean your carpets properly to extend their lives and improve your air quality, but between cleanings, your issues will not be as apparent to visitors. If you keep your eye out for this discoloration, you are going to notice it before anyone points it out to you.
Actual Solution: Carpet Cleaning
A carpet cleaning service can take care of the difficult messes like filtration soil. It is not just the placement of the soil that is going to give you an issue with standard DIY cleaning methods. In most cases, the oily nature of the substance is going to bind to the fabric fibers, requiring steam cleaning.
Steam cleaning is helpful for a variety of cleaning services, and filtration soil is certainly one of the stains it is quite effective at cleaning. The heat and pressure separate the soil from the fabric. Turn to professional carpet cleaning every six months to a year, depending on your level of exposure to filtration soils.
Final Recommendation
These dark streaks are going to come back, just like dust is going to come back. Cleaning is a constant uphill battle, but knowledge is the best weapon against the mounting messy attack. Keep in mind filtration soil is just what is floating around in the air! Many other substances are trying to leave lasting stains on your carpet.