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black dust on my walls

The phenomenon is called ghosting. Usual suspects include poor combustion or venting in gas fireplaces, burning heavily scented candles, oil or kerosene lamps, or having your house under a negative pressure. Rugs, carpets act like filters, and you can see soot lines that follow the seams in the subfloor or blackened carpeting at door sills. Poorly sealed ductwork is another culprit. If you live near a major highway, soot emissions from the traffic can be a contributing factor.

By all means, have your combustion equipment checked by a pro. Soot can also mean the other products of combustion like deadly CO gas can be being pulled into your house. Adequate combustion air must be provided for any fuel burning appliance. Here is a quick test. Close all doors and windows. Start all exhaust fans in kitchen & baths, clothes dryer, any other vents. Go down to the basement, open one of your basement windows a crack, then hold a strip of tissue next to the opening. If the tissue strip indicates that air is rushing into the open window, you may need more ventilation or combustion air. A pro can offer several options to provide adequate combustion air. Also, your ducts should be checked, and make sure that your air filters have been regularly changed or cleaned.


  • bob peterson
    bob peterson Member Posts: 1
    black dust on walls and appliances

    I have had a black dust like substance an my walls and appliances since I turned on my heat this year. It seems to almost pattern the studs behind the walls,also the nail heads. I do not believe it is mold, Im cannot find a source of moisture that would explain that. I was told that it may be bad burner. Can anyone tell me what this might be?
  • Brad White
    Brad White Member Posts: 2,393
    Any number of things

    if you burn oil (even gas sometimes) soot is created. A leaking heat exchanger can release some into the airstream. Is this an air system, water or steam system?

    The "ghosting" you are seeing is classically on uninsulated walls. The pattern follows where moisture in the air, any amount, condenses or coalesces around dust particles and cling to the colder surfaces, thus transmitting the pattern behind. Insulating walls can minimize if not eliminate this.

    But the fact that you have soot at all is more of a concern. Call a pro and get that beast checked top to bottom. Today.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
  • Chris_82
    Chris_82 Member Posts: 321
    Do you have Plaster walls?

    In the past, old plaster and some drywall will collect dust if air is passing thru it. Most think that air can't get thru solid walls but it does, nail holes and poor attic insulation also contribute to this and where you find dark lines or collections of dust is where the most air is passing. get into the attic and fill any holes in the plates with foam. If you have a furnace or oil make sure your heat exchanger or collection plates are ok, no holes in them. And be especally carefull to check all of your vent piping especially places you can't see. When was the last time your chimminy, if you have one was inspected? Do you have a wet basment or crawl space? Mold forms rather quickly find out what it is before it gets any worse. Generally soot and dirty air, which is natural air in homes anyways will smell, wheras mold will stain the walls and have to be cleaned off as compared with simply dusting away. And do you have a CO detector? Make that a priority as well.
  • jim lockard
    jim lockard Member Posts: 1,059

    Is you a candle burner? Just one candle has the abilty to soot up a house.Them big candles that smell right nice is the worst J.Lockard
  • Bob Harper
    Bob Harper Member Posts: 986
    Black Particulate Matter

    Please search the archives on this site as we have discussed this phemomenon at length. Just keep in mind, until you have a reliable lab report, you don't know what this stuff is. Call it Black Particulate Matter (BPM). I used to investigate BPM claims for a mfr. Trust me, it is not always "soot". Even if it is soot, what kind? Is it a short chained aliphatic hydrocarbon soot as from gaseous fuels or from long chain aliphatic solid or liquid fuels? Is it from wood burning? Maybe it is mold, dirt, charred food particles, from cigarettes (I've seen both right and left hand cigarettes), metal filings from door hingles, etc. Lots of potential sources.

    Find the source first, then that will help explain why it deposits where you find it. Then you can plan on clean up. You can do this or you can file an insurance claim. They will then subrogate to the most likely culprit while you get a clean house.

  • J.C.A._3
    J.C.A._3 Member Posts: 2,981
    All GREAT suggestions !

    I would especially pay attention to the chimney being either lined or sealed completely.

    I worked on the waterfront for a long lotta years, and the last town I worked in had a coal fired, electricity plant, right across the harbor. The dust from both the delivery and burning of said coal, worked its way into many of the homes that were once summer "camps" and mostly uninsulated. Once the property values increased enough, they were turned into HOMES, but were still vulnerable to the same effects of the plant.(The cooling and condensing on the studs and nailheads was a good thing while trying to hang baseboard, but I digress!)

    Another thing that made the same thing happen was....dirt basements. Air doesn't much care where it comes from, and when these homes were tightened up...some of the infiltration was being drawn from the dirt floors in the basements. With cooled and moist walls...the "dust" stuck to them like a lawn dart!

    More than one time I had Service-Pro call my old company to test a boiler/furnace because they determined that the "Ghosting" was soot. Rarely, but occasionally...they were right.Most of the time it was something from an outside source...but at least they called to MAKE SURE.

    Lifes lessons also say that burning candles is a big contributor. (but I only burn 1, and its in the living room!) Soot don't care much either..it'll settle wherever it so desires. Like most of us...It's lazy, and is looking for the easiest place/way.

    Check and test the heating system to make SURE that it isn't the cause....but when it's found that it isn't, always have a plan B to look at. Chris
  • Jim Bennett
    Jim Bennett Member Posts: 607
    Copy and Paste...

    this link. There was a HUGE thread relating a similar problem.

    Jim Bennett
  • clammy
    clammy Member Posts: 2,983
    ghosting/aquastat sertting

    i have seen this a few times and on one or two cases it ended up being a high aquastat setting like over 200 it seemed to increase that convention across the baseboard and creat these black ghosting on the walls ,the one home in question had no smokers,insulated outside walls ,i lower the aquastat down to 180 they re painted and there has been no ghosting since and it's been 2 heating seasons and no calls peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
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