Carpet Staining

[Mike Lamb]

The second floor of this 1982 home had dark staining at the carpet along the perimeter of all walls. Interior walls, exterior, closets, etc. I would describe it as soot so I'm thinking candles and more candles with negative pressure but I don't know.

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[waynesoper]

lack of vacumming and cleaning. They were slobs.

[randynavarro]

Air movement between floors and walls.

When the HVAC (or exhaust fan, or window fan is exhausting through a window or anything that creates pressure differentials in each room) is running, air is getting drawn through the carpet.

The carpet is actually acting like an air filter.

Diagnosing exactly can be a bit tricky.

One guess: the bedroom doors are tight to the floor thus blocking return airflow to the central register. The air is trying to get back to the air handler via some path. . . namely the areas you're seeing as dark carpet.

[MMustola]

That is pretty common around here. They use the space between studs and joists for cold air return ducts. The edges of the carpet act like a filter causing those stains along the baseboards

[Mike Lamb]

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Maybe. But the main runway and foot traffic areas etc. were clean. This stuff would not be clean no matter what shampoo you use if they were general slobs.

[Mike Lamb]

Thanks, Randy, Mark and Wayne.

[Rocon]

This is a very good article about ghosting, and filtration.

http://www.buildingscience.com/document ... m=ghosting