Carpet staining

[tech119]

Hopefully someone out there has heard of this before... I have a customer who has light colored carpet in her home, and for some reason on the second floor there are black marks all along the walls. Two local carpet companies have said that it is caused by "an hvac system imbalance"; in other words, a positive or negative pressure on the house causing infiltration or the opposite. I find this hard to believe, because there are no marks on the carpet downstairs, and normal dust, be it from infiltration or other, is not black. Does anyone know what is happening here?

[tinknocker service tech]

induct line coming loose
cheap carpet
oil burner with cracked heat exchanger
dirty as hell filter
dirt in the ductwork
and cheap paint

[m kilgore]

Are they burning candles. This will cause the black marks for sure.

[Panama]

Exterior, interior, or all walls?

[tlcartman]

Originally posted by m kilgore
Are they burning candles. This will cause the black marks for sure.

we have a bingo. look at the electrical outlets, are there dark streaks going up from them?

try this link
http://www.homeenergy.org/archive/he...98/980109.html