January 17, 2020
Posted by D. A. Burns
Sometimes a Frequently Asked Question regarding installed carpet keeps getting asked, and sometimes we can add a bit more to the answer.
Christina in Clyde Hill asked: What are these dark areas next to the wall?
Terri in Greenwood asked: What is this dark square that matches the dresser?
Michael, Downtown Seattle says, “There’s a “lightning bolt” shaped dark area appearing on my area rug. It starts under the dining room table and ends in the middle of the living room. What could this be?”
Jess in the Renton Highlands told us, “A heavy dark discoloration started to show up at the sides of the stairs to the lower floor in my new house. It keeps getting bigger … how do I stop it?”
John on Lake Union says, “I have fabric panels in my boat that have speakers behind them. I’m beginning to see dark areas that match the shape of the speakers. Can you fix this?”
We’ll address each question below, but the title gave away the answer; all of the above installed carpet conditions are considered filtration soil. Filtration soil occurs when carpet or fabric acts as a filter when air passes through, leaving some dust and oil behind.
Air movement in a home may be caused by furnace and other fans, although there’s a theory that air expands on the sunny side of a house and is pushed to the cooler side, and then pushed back as the house and sun change positions through the day. Natural convection occurs as warmer air rises, and any opening in the construction of a floor will allow air to flow through from lower floors.
Clients often mention that they never saw soil filtration lines in their old houses, and wonder if poor construction practices are to blame. It may be the opposite, as old houses tended to be drafty, while newer homes are more energy conscious and tightly built to prevent air leakage to the outside, the air moves through the interior of the building. Higher pressure areas no longer push air outside.
The soil or dust may consist of pollen, shed skin particles, tiny bits of sand, oils from cooking, candles, or outside air pollution. Together these soils combine to form a sticky substance just right for adhering to fibers. A little soil deposit can quickly become noticeable as the area fills with ever more dust-collection adhesive. Eventually, the oils will oxidize and turn yellow, and will become more difficult to remove.
If you see this filtration soil beginning to happen, giving this area of carpet a good vacuuming is a start. If soil discoloration remains, apply a detergent that is safe for your carpet type, agitate with a white towel, blot and rinse. Rinsing is important, as any detergent residue left in the carpet may attract more soil.
Stopping the problem isn’t always simple, as the answers to our customer’s questions indicate:
What are these dark areas next to the wall?
That’s where air is flowing. It may seem odd that the easiest path is under a wall, but remember that the ceiling and wall corners are all sealed with joint tape and paint, while the unfinished base of the wall is only hidden by trim molding. The cure in this case is to have the carpet pulled back so the gap at the bottom of the wall can be sealed with caulk. When the carpet is re-stretched, the discolored area can often be trimmed away.
What is this dark square that matches the shape of the dresser?
A furnace vent was under the dresser. The dresser had low legs and an open base, but created enough back pressure that air flowed through the top of the carpet nap. In this case the dresser was moved away from the vent, and we suggested the furnace filters be checked as well.
NOTE: We often see filtration soil around the edges of air vents and even tiny dots from holes in the carpet backing that occur during normal installation. Stopping this might require caulking the edge of the vent so air can’t flow under the carpet.
There is a “lightning bolt” shaped dark area appearing on my area rug. It starts under the dining room table and ends in the middle of the living room. What could this be?
Most likely this is the “high-rise condo crack.” More recently constructed high-rise buildings have floors made of poured concrete. This is good for fire and noise resistance, but concrete often gets hairline cracks as they cure. There’s no structural weakness, the crack just creates a place for air to move between floors. Given a higher level of exterior pollution downtown – and the dynamics of moving air around a multi-level building – this kind of filtration soil mark is not uncommon.
Sealing the crack eliminates the air movement.
A heavy dark discoloration started to show up at the sides of the lower floor stairs in my new house. It keeps getting bigger … how do I stop it?
Since no one walks on the extreme edges of the stair carpet, builders often cut the stair treads and risers short of the walls. Sometimes the gap is big enough to put your hand in, so normal caulk may not work. Use of an expanding foam, inserting foam “backer rods” followed by caulk, or old fashioned trimming wood to fit into the gap may eliminate the filtration soil condition.
In Jess’ home, the rapid soiling was partially due to the garage being in the lower level. She was in the habit of backing her cars into the garage (one with a diesel engine) which meant a little more soot than normal was added to the indoor air.
I have fabric panels in my boat that have speakers behind them. I’m beginning to see dark areas that match the shape of the speakers. Can you fix this?
We can fix it, temporarily. Each of the speakers is a little air pump, pushing air back and forth through the fabric thousands of times with each listening. Hidden speakers are undeniably cool, but they will require some cleaning to keep them hidden.
Other fabrics are also prone to showing filtration soiling. Hanging banners, drapery fabric, tapestries and upholstered wall panels also end up being air filters and need vacuuming to stay looking their best.
So now you know what filtration soil is, and whether you can stop it … or just have to manage it. Good news if you’re working with D. A. Burns for cleaning. We don’t charge extra for working on filtration soil – it’s included in our service.
Tactile Speaker, courtesy of Eunee Jo.