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Air Quality report

KazTech Member Posts: 2
Hello everyone,

I am in the process of purchasing a home, and I had a air quality test performed. The mold value came back as 20 ng/L, which seems to be in the "moderate" zone. My daughter had an allergy test performed a little while ago and it came back that she has a slight allergy to mold, they did not specify which type. The report says that moderate means "Actively growing molds are present, individuals sensitive to molds will likely be affected.", this was concerning to me.

Some things to take in account of this sample and test:
  • Only one reading was taken, and it was from the basement
  • Walk out, unfinished basement.
  • The house has had a mold issue in the basement before, but had been remediated, and a test was performed after to show that it was successfully removed.
  • Home is in Southeastern, PA (suburb of Philadelphia)
Some of concerns and questions:
  • I know its probably impossible to determine via the a forum post, but is this level something to be concerned about? Speaking mainly to the basement is not a high traffic area, does this reflect the mold values in the rest of the house.
  • If I make the basement as dry as possible ( use of dehumidifier, installation of return ducts in the basement, installation of UV lights in HVAC units, All things I am willing to do) will this assist in considerably lowering the mold readings? The concept was killing the moisture might kill most of the mold.

The house fits all other requirements, but obviously my daughters health is the highest concern of all. I acknowledge that you all don't have nowhere near the complete picture, but any advise or feedback is more than appreciated.

I have included a snippet of the report, if more information is needed please let me know.

Thanks in advance,



  • Jamie Hall
    Jamie Hall Member Posts: 22,100
    There's mold and mold, of course. However, I think you are probably right to be concerned. Mold, however, will only grow where there is moisture. Therefore, the thing to do is to address the moisture issue in the basement.

    First question: is the basement leaking water anywhere, or the floor or walls damp? I presume this is concrete? If it is, you probably won't get far unless the basement walls can be waterproofed, and foundation drains -- which should be possible with a walk out basement -- are in place and are known to be working.

    Then your overall approach makes sense, but I would recommend that the basement be included -- via proper ducting (sounds this is forced air) in the conditioned envelope of the house. Do NOT rely on the furnace taking air from the basement! Give it proper ducted returns and proper supplies to all areas, including the basement. You may find you need to add dehumidification, either in the forced air system, or stand alone; you need to keep the relative humidity down -- 50 to 60 percent is amply high, even in the basement. The UV will help.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • KazTech
    KazTech Member Posts: 2

    First thanks a lot for your response.
    Some answers to your questions:
    • No there was no noticeable dampness on the basement walls or floor. (you are correct, concrete walls and floor)
    • This is a forced air system, two unit, one for upstairs and one for downstairs.
    Some further questions:
    • By putting returns and supply registers in the basement, does that give the mold more chance of spreading to the rest of the house? Or with the combination of registers in the basement and UV lights help considerably to lower the humidity as well as kill the mold?

  • Jamie Hall
    Jamie Hall Member Posts: 22,100
    With regard to the question, yes, it would give the mold a chance to spread upstairs -- but it will anyway, if you don't control it. What you need to do is to make sure that that basement space is in fact climate controlled -- both humidity and temperature. And the way to do that is with proper, controlled, supply and return ducting, sized and located to make sure that you have just as good air exchange and circulation -- probably better! -- as you do upstairs. Then you can get it dry enough so that the mold doesn't have a chance. You can filter and zap the air with your blower system, and get the temperature right, and control the humidity. Otherwise the basement is sort of catch as catch can... which never works properly.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • BillW
    BillW Member Posts: 198
    Mold is virtually impossible to avoid. Even the "clean rooms" in electronics and pharmaceutical companies have at least trace levels of mold. Mold reproduces by sporolization. A "bud" called a "fruiting body" grows on the main "root" of a mold organism and eventually fills up with spores which then are released into the air thru some kind of trigger event, and then float around until they land on a suitable substrate and begin to grow. Some mold spores are so small that they can remain airborne for months, held up the molecular motion of the air. Mold needs food and water. You can eliminate some food sources like cardboard storage containers and other paper or cloth items, but wood and just about any other organic substance can support mold growth. You can control the humidity with de-humidifiers, controlling the temperature and circulation, like Jamie suggested, and I would consider a heat recovery ventilator. They tend to dry out a space. It is needed in the basement anyway, so it would be in a temperature controlled space and you can easily route the drain line to the sump or a condensate pump. A ventilator can be used to keep the basement under a slight positive pressure, and is frequently used for that in radon mitigation projects. Dry-Lock paint on the walls may help, and sealing the floating slab (if you have one).