Seeing that no one took that bait, I'm completely spitballing here:

It seems that the technique used by this pest abatement contractor is the "apply pesticide everywhere and hope that you'll be sure to kill everything that might enter the structure from the soil" technique. I admit to having a question if that is strictly really necessary. Rather, it seems to me that a properly installed crawl-space radon depressurization barrier should:
1) if intact, be proof against pest entry across that barrier and through the barrier-foundation seal.
2) but if such a barrier is compromised by pest entry, it seems to me it should show evidence of such breaches relatively clearly, which can then be addressed.

My recommendations would be:
1) Find out if this pest-abatement contractor's approach is uniform across that industry or if not, find out how other pest-abatement contractors handle the issue. Perhaps they have a more surgical approach of applying pesticides at the points of infestation rather than to the entire structure.
2) Find out if any pest-abatement contractor with an open mind about possibly changing their abatement technique would be willing to work with a similarly solution-oriented radon mitigator and do some pre-/post- experimental work in a few buildings, if the homeowners would be willing to cooperate.

OK, Henri, I missed this when you first posted this, but I'd sure support your idea that anyone familiar with this issue should come to Texas and make a presentation. I hadn't been aware of this problem, but I can't imagine that some of the radon professionals in the field haven't already been involved. It would be good for paleontological curators to be able to attend Symposium to pick some of the brains of the most expert mitigators in the business.
I note the article you cited gives the reference here that describes the geochemistry of what's happened: https://www.sciencedirect.com/science/article/abs/pii/S0045653521019160?via%3Dihub
Amazing.

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!

Thanks, Jeff, for your contribution. I hadn't been following Doug's thread. I wasn't aware that EPA had such a list that was a reasonable attempt at being comprehensive, even if it's not necessarily updated.
Much better than my own rough answer (given in a separate thread).

Hello Jeff,
Sorry I missed your initial posting.
I am not aware of a comprehensive up-to-date listing of all jurisdictions that have adopted Appendix F. One good reference for state laws is the Environmental Law Institute's posting at https://www.eli.org/buildings/radon-control-new-home-construction
There are also some localities than have moved in this direction, ranging from
https://www.manheimtownship.org/1204/Radon-Mitigation-Systems (just up the road from where I live) to more western places such as https://www.fcgov.com/building/pdf/appendixf.pdf and https://www.ci.wheatridge.co.us/280/Adopted-Codes-Amendments
Even though there aren't that many places that have adopted this voluntary appendix as a new-construction requirement, the point is that it's not an earth-shattering thing to have done. I haven't heard of any issues arising in places that have adopted Appendix F. It appears to be accepted as just one other thing on the list of code items to check off.
I am happy to work with any Lung Association staff who has the bandwidth to devote time to working for the adoption of radon reduction policy measures, but I do recognize that local priorities are not dictated by me. Similarly, I am sure that AARST would be happy to support local membership working on state and local policy development.

Issues such as short-circuiting and animal occupancy notwithstanding, I'm always interested in results. Did installer have pre- and post-installation (both preferably longer term) testing? Also, some CRM results from a central location would be very interesting to see. Did you get called out because "My radon level is still high and I just can't understand why my system didn't fix it."?

Colleagues,
Attached is the Flyer for the Radon Testing in Schools Webinar.
Please distribute as you can.
Thanks!

People are probably waiting to see your on-site data before commenting. :smile: All I think of: Is PFE confirmed? What cfm is that fan drawing at what pressure difference? Is permeability under crawl too high? Do you have unaddressed sources in the adjoining porch and garage? Good luck!

Bill, your table always shows the higher value of each pair first, so not sure which wells showed decreases and which ones showed increases.

Hi Rob, I happened to notice this request hanging from months ago and I felt bad that you had had zero replies, a little unusual for this list. Not that I had any great advice to give at the time, but wondering how things worked out for you on this? Did you get a good solution? Could WVDHHR's radon office help?

Congratulations on your detective work and on being rewarded for your application of first principles! (Glad it was none of the wild scenarios I and some of us were thinking of.) Those large but hidden breaches through the slab under tubs and showers keep showing up in "houses from heck," so this is a good reminder for mitigators not to forget to explore the existence of those, if not too much trouble, even before doing the first round of post-sealing PFE testing. For example, fixing those first perhaps could reduce the need for a more powerful fan even if a system might have "worked OK" without addressing those gaps.

And yes, there are such telemetry devices as you're asking about on the market, and I anticipate that these will become more common, as folks become more and more accustomed to the "Internet of Things." I leave it to the experts to discuss their costs, capabilities and limitations.

Others above have expressed thoughts so well, but for those who'd want to read a bit more, here are a few things:

- It's been an honor to be the recipient of Bill's generosity of spirit, ranging from my first conversation with him in the 1990's when we got into our same-hometown (Lancaster, Pa.) connections, to helping my son Henry track down a high school radon-related science fair topic (Tn!) and mentor (Dan Steck!), to even just earlier this year, taking the time to manage the onerous QAPPs process for work on the radon disparity metric.

- We've just shared the following with the NRAP Leadership Council:
We mark the passing of R. William “Bill” Field on November 4 with sadness for his passing even as we recall him with great admiration. Many of us working on NRAP knew Bill personally and found him to be a visionary expert on radon, the most productive worker, a tireless advocate, compassionate, generous and easy-going as a person, and a dear friend. The world in which we work on saving lives from radon would be a much more difficult one were it not for Bill’s life of scientific research, perseverance and championship over the decades. Think not only of the Iowa Radon Lung Cancer Case-Control Study, the President’s Cancer Panel Report, the World Health Organization’s Handbook on Radon, the Health Care Provider’s guide and numerous studies, reports, and presentations, but also of Bill’s willingness to take the message of what all that science meant, to put it into human terms, and to use his deep knowledge and professional reputation to call for the kinds of policies that would save lives from radon-induced lung cancer.

- Finally, I close with brief excerpts from my last conversation with Bill, about only three months ago...
Bill: "Trying to hang in there. Completed 3rd chemo with a good many issues...."
Kevin: "... I will bother you with things radon only as much as you feel it’s useful to be distracted by them.
In other words, no obligation if you get any email from me on the subject...."
Bill: "Thanks Kevin, I am still working on projects (two NIH R01 grants) at Columbia part time. It is a welcome distraction. Be well."
That last reply sums up the man pretty well, I'd say.

An amateur here with some thoughts in the hope that one or two might be helpful:
Agreeing with Bruce's maxim: "Take a whole-building approach until you show it's not." This tack suggests that there might be other pathways than around the slab or through joints/cracks, etc. Hidden utility chases, who knows?
Re Shawn's: "Can you share a drawing with the data?" Yes, the experts (not me) on this list can give you a lot better advice if they can also see all the details you have.
Re Doug's comment: "All areas checked have shown neg. pressure below the slab." Are there any areas you haven't tested yet that could reasonably explain those high radon levels? Are there any diurnal/meteorological reasons to suspect that your neg. pressure values do not remain stable? And perhaps you don't need to go to the trouble of making test holes everywhere if you would first use IR vision to look for any obvious places of incursion of soil gas?
Re Bruce's comment: "Is the rock system with the caves that the site sits on exposed to a cliff face anywhere in the near vicinity. Could wind pressure be messing with you in a strange way?" Makes me think that shared variability in the behavior of multiple simultaneously run CRMs, tracked along with met. data, could indicate some pros and cons for that hypothesis.
Re Doug's comment: "...before drilling and some testing of the concrete for emanation." I'll take this to mean that you'd be hypothesizing that the concrete itself is the source. Unless you have experience with that happening in your locale, or if this site is a former radioactive tailings dump, I'm inclined to think that radon levels you found are too variable / too high at the high end to think this explanation is likely. I'd save the emanation question for later unless there's an easy-to-do standardized procedure for determining if it's significant (Bill Brodhead, what do you think?).

Janice Nolen - 2020 -- Rose to prominence from her work with American Lung Association of Tennessee.
Susie Shimek - 2022 -- Rose to prominence from her work with Tennessee Radon Program
I like to suppose that now they are happily catching up and comparing notes.
The Volunteer State has certainly been home to some great environmental health champions.

As a participant representing public health interests on some of the ANSI/AARST standards commmittees (not Mitigation), I do want to underscore the following:
- We are all in the business of saving lives from radon, and strong yet reasonable standards of practice adopted and implemented across the country not only can ensure that lives are indeed saved, but also can help protect the radon industry from legal and commercial challenges.
- In my experience, the process of developing standards has always been one that seeks input from beyond the committee membership, particularly if that includes illustrative science and evidence from practitioners. As Dallas has shown above, standard-setting is intended to be open for all to make contributions at https://standards.aarst.org/public-review/ and I do strongly encourage anyone who has recommendations for what the standards should say to provide specific language for such changes along with a cogent accompanying rationale.
- The principle of the standards requiring only what is needed for safety and effectiveness is something that has always been a touchstone for our work. We certainly recognize that a standard that's "perfect"--and hence, too complex or too onerous, and so is too difficult to follow or is not even used--is a worthless standard. That's why, in our meetings, standards committees are most eager to hear from stakeholders who represent those in the industry who would actually have to live and work under the standard. I have seen proposals simplified and improved after someone active in the field made exactly that sort of commentary.
- If any radon professonals want to be more involved in the standard-setting process, such as by devoting time to advise standards committees, that kind of interest is certainly welcome: https://standards.aarst.org/participation-in-aarst-consortium-radon-standards/

Henri,
By those replies, it looks like the walls are the big suspect.
I'm only a sidewalk superintendent in this particular area of expertise, so I leave it to your judgment if I know only enough to be dangerous...
For one thing, I do wonder what the tenant would find acceptable, since it may be possible that even if averages are kept quite low, that may not prevent every possible brief excursion above 4 pCi/L. Also, wondering what the radon level is the tenant's current location elsewhere.
Curious if you're doing surveys (grab sampling, air movement, not just PFEs) at different points near the walls to get a better sense of source location(s) and pathway(s)?
The sensitivity of the home to rapid peaks also makes me wonder if there is any overpowering (karst?) phenomenon that is sometimes at work. Did you any see diurnal behavior patterns?
Even wondering about any unusual direct sources of radon--recalling I heard (or is it not the case?) that radium salts were found to be efflorescing onto the basement wall of the Index House. What is your gamma microR meter showing?
I'd be tempted to say "Well, just directly mitigate that apartment with a dedicated system installed in the corner diametrically opposite the first," but apart from any impracticalities to doing that, unless you adequately characterize what the real problem is, I admit that would just be "Poking and Hoping."
In any case, be sure to communicate to the owner and tenant that you are consulting with other professionals about this unusually difficult case, all of whom want nothing more than for this mitigation to end quickly and successfully.

Bill's paper is excellent in showing both the sensitivity of actual RDP levels to environmental conditions and the ease with which one may interfere with RDP measurements.
Given that the majority of folks--e.g., homeowners, purchasers, real estate agents, et al.-- involved in decision-making around radon testing and mitigation are not scientifically trained, it seems best to continue with the primary focus remaining on first reducing radon levels, preferably to below the strongest defensible action level, and only then looking to RDP reduction as a further exposure-reduction intervention.
In most cases, there are simply too many variables associated with RDP control for me to support reliance on it as a technique subsituting for radon gas control--in other words, second-line and supplementing it, yes; first-line or replacing it, no.

Thanks, Leo. Exciting stuff.
Apart from the essential prevention work you and other professionals do, this is the kind of thing we're always hoping will emerge from research - reliable earlier detection with lower risks and costs.

P.S. Although I could not locate a copy of this item referenced in Doug's attachment:
Hopke, P. Studies on the Performance of Air Cleaners and their Optimal Reduction of Dose from Radon Progeny, EPA Cooperative Agreement CR-820470, October 5, 1992-1996.
I did find this article by Hopke et al.:
https://www.tandfonline.com/doi/abs/10.1080/02786829308959635

That's excellent stuff, Doug; I'm so glad you jumped in here. I highly recommend that readers listen to the excellent interview Doug did with Dr. Hopke. I definitely learned some things that refined what I may have first picked up on this topic as long as 30 years ago.

For me, one part of the interview summarizes the findings at the time very well, as Dr. Hopke was discussing how well (or not) he found different air cleaner methodologies worked: "...we had some cases where there was no reduction in dose because of the changing [particle] size distribution. There was no case [among the units studied, of course] where the dose increased. In most cases, the reduction in dose was of the order of half what the reduction in exposure was." In the cases studied, a common exposure reduction was about 50%, with the corresponding dose reduction being about 25%.

In other words, although the ratio of "unattached fraction to attached fraction" would have increased with application of the air cleaning technique, yielding an altered particle size distribution that may have posed higher risk when measured by the ratio of dose to activity (e.g., mSv/WLM), the fact remains that total activity (WLM) was reduced sufficiently that dose itself never increased, but rather typically decreased.

Finally, I also want to emphasize that Dr. Hopke very strongly recognizes that testing and ASD mitigation is the first line of defense, but I think it could well be that the role of proper air cleaning methodologies as an adjunct or "trim method" may not have been given its due.