Black Stain on Carpet

LESLIE: Micki in South Carolina, you’ve got The Money Pit. How can we help you today?

MICKI: I have two outside bedrooms and a den area.

TOM: OK.

MICKI: And it seems like the carpeting near the wall, on the outside, has black on it.

TOM: Right. Mm-hmm.

MICKI: And in a few areas, it has come into the room a little bit further.

TOM: Yeah, you know why that is?

MICKI: No.

TOM: Here’s why. What happens is you get warm, moist air inside your house; it hits the cold, exterior wall and it falls. As it does that, it picks up the dirt that’s in the air and it brushes it against the carpet. And carpet, of course, is a great filter material. So that’s why you get this black staining sometimes on walls or on carpets near the room edge, because of the normal convective loop of hot air rising, striking cold windows and walls and cold air falling. It sort of washes the dirt, sort to speak, against the carpet. Sometimes it sticks and it looks kind of nasty. So this is really just a cleaning problem. It’s not indicative of anything more than that.

MICKI: OK. So I have a lot of allergies and I wanted to make sure that it wasn’t something that was kind of …

TOM: Well, if you’ve got a lot of allergies, Micki, carpet is not the best choice for you because it really does harbor just about everything that is bad for you: dust, dirt, dust mites, things like that. If you’re going to have carpet, though – you have a forced-air heating system, right?

MICKI: We have gas heat.

TOM: Yeah, but you have ducts, right? You have hot air ducts?

MICKI: Ducts, yes.

TOM: OK. So what you want to do is you want to get a good-quality electronic air cleaner. There’s a product by Trane called CleanEffects and it’s excellent at filtering out all of the dirt, all of the dust, even down to virus-sized particles of dirt. You really want to invest in a good-quality electronic air cleaner when you have allergies and, if at all possible, try to minimize carpet in your house because it just is a big, fat filter for all kinds of dirt and dust and mold and dust mites.