• Scott Bacon
    1
    I have a house that we originally mitigated about 12 years ago. I was contacted by the owner a few months ago as her Airthings was reading 14 pCi/L. We added 2 more suction points to the original system. This brought the level down to 7 pCi/L. We then conducted a bucket test on the concrete which came back at 7 pCi/L. We added a second system with 2 additional suction points. The radon level then came down to 6 pCi/L. PFE testing shows .006-.010 in/WC, so there seems to be plenty of negative pressure across the slab. There is 1 granite countertop in an upstairs bathroom, but no other natural stone in the house. Radon levels on the first and second floor are 6 & 4 pCi/L, respectively. There has been no construction or remodeling done on the house since the original install. Would 7 pCi/L of radon coming from the concrete cause any of this? Testing has been done using a tripod, so the tester is not on the floor. The house is a early 1900s build with concrete block walls and poured concrete floor.

    Any ideas or help would be greatly appreciated.
  • Kevin M Stewart
    94

    Hello Scott,
    Sorry for the lateness of this reply, but hoping you at least got some off-line responses to your question.
    My thoughts, solely as an amateur, but having kept my ears open over the years:
    1) Just to be sure, you were confirming the Airthings results with independent devices/instrumentation? Many such devices certainly provide valid results, but all it takes is one "bad apple" to have you chasing after a phantom.
    2) Curious if you have any idea what the ACH for the building is? Any sense of what airflows are like (volume rate and direction) through the envelope at different levels in the building?
    3) For most buildings, I can't imagine that a bucket test on slab of only 7 pCi/L would be indicative of any serious infiltration or emanation, especially if your PFE is showing up to be good in the correct direction. But I am getting out of my depth here and would appreciate a real expert chiming in authoritatively.
    4) The main suggestion I have is to do a series of samples that help you focus in on sources better. These would include:
    a) Some IR imaging of surfaces that are soil-contact or of points that are possible pathway egresses. There may be some unusual point of entry that you've been missing, even with your PFE testing.
    b) Some grab sampling for radon or progeny activity in a good variety of areas. I'm not suspecting the granite at all since the upstairs radon is around the typical ratio with the lower level's value.
    c) Pay good attention to checking around those odd "extra-slab" areas such as entry pads, patios, garages. They can be (per Brodhead) their own high-radon micro-environments that can have a surprisingly outsized effect on internal levels.
    d) Consider some gamma sampling if the above isn't helpful and you are still concerned about gross contamination, e.g., of building materials with Ra-226.
    Good Luck!
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