In researching the subject of Radon mitigation, I came across this article, Titled "Radon - A brief discussion", by Caoimhín P. Connell (Forensic Industrial Hygienist)

Please read that whole article before posting any comments. It's a long read, but I'd like to ensure everyone who comments on this topic has in fact read and understands the article. No biases please! :)

The first paragraph states the following:


A large portion of the general population is under the misconception that the frequently published risks associated with radon are well accepted scientific facts. In reality, the vast majority of well designed studies do not support policy or positions that exposures to indoor radon pose a significant threat to health, and indeed, the majority of those studies indicate that, at concentrations typically seen in homes, as the level of radon increases, the risk of lung cancer goes down, not up.


After reading the science behind Caoimhín's well-written and thorough article, I have to say I agree with his words and message. So what does that mean to an energy auditor? What advice am I to give to a homeowner whose home is under constant depressurization causing backdrafting with their woodstove or failing to pass worst case combustion safety tests, all because of their radon fan in the (nearly-conditioned) crawlspace? I realize as a BPI graduate I am supposed to consider Radon. But what do I tell folks whose Radon mitigation system indicates levels far below 7 picocuries? Should they run that fan that consumes 526 kWh/year, costing them $70/year?

I welcome your input. Love this community!


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I noticed that the bulk of the references used are back in the 70's & 80's - just how old is this piece, does it take into account anything new? For example... I find it interesting that while smoking rates continue to decline in this country, lung cancer continues to increase.

As for how to consider radon - use your head & remember do no harm:

Next thing to remember is that ventilation is not about saving money, it is about health, safety & comfort

I use my head all the time, which is why I ask questions when something seems askew ;) By "askew", I mean blanket statements from governmental agencies like, "Depending on the set of assumptions used", or, "estimated risks", based on poor science. Where is the science?

This is exactly the point the author is trying to make, that the political organizations who have put these standards into place are basing their policies on documentation and science that is either antiquated or scientifically wrong. I couldn't quite determine when the article was written, but there is this blip:


Although political organizations (such as the US EPA) publish a variety of statements of elevated risk, to date (2010) there are no scientific studies that have ever actually shown that radon gas, as typically seen in houses, increases the risk of cancer. To be clear: There are NO valid studies that have conclusively demonstrated that typical residential exposures to radon increase the risk of cancer at all.


So, it's at the most, six years old. New enough. Certainly newer than the "studies" the EPA uses for its "science".

On the subject of "do no harm", aren't the Radon mitigation folks doing harm when they create a significant negative pressure in a home that causes woodstove and/or combustion appliance backdrafting? And when we install unbalanced ventilation systems (sucking the air out), which seems to be the solution for so many building performance contractors, aren't we just exacerbating the problem? Why not rip out the Radon system and put in a whole-house balanced HRV/ERV? That's a win/win for everyone, right? Why don't Radon mitigation folks do this in the first place? There seems to be a disconnect.

Let me just state "use your head" does not mean you are not, you are questioning which is good. The catch is sorting through & using the best info possible

As for mitigation doing harm - not even close as it should only be causing negative pressure under the slab. If this is causing issues inside the house with depressurization, you need to find that issue & fix it, because it shouldn't be that way.

Next having naturally drafted appliances in a house & saying it is safe is the worst lie that I can think of & costs (probably / most cases) more money than running the fan as you are continually exhausting conditioned air out of the house

Exhaust only ventilation - yes that does exacerbate the situation which I wrote about here: - but heh, you want to talk about unfounded basis for doing things, welcome to another one. Just like many things, use your head and make your best judgements - in my case I make sure the units can meet the standard but don't run them as long generally & oh yes if they show high enough radon concentrations - mitigation it is (passive should already be built in)

I also wanted to point out something I found this morning while doing more research on this subject.

Have a look at and scroll down to "Report: EPA's Assessment of Risks from Radon in Homes" and notice this wording...

The Agency's updated calculation of a best estimate of annual lung cancer deaths from radon is about 21,000 (with an uncertainty range of 8,000 to 45,000)

An uncertainty range extending over double the estimate of what the EPA advertises as "fact"?! That's reason enough to negatively pressure millions of homes, potentially causing other health issues as a result? Is that Radon system pulling blown fiberglass insulation particulates down from the attic?

The more I investigate, the more I discover how much dis-information is floating around out there. But by whom?

Reading through 578 pages of that book now. More to follow... (see

If putting the house under positive pressure using fresh air helps mitigate not just radon, but thousands of other air quality risks as well, the conclusion to be drawn is radon systems are placeebo offering consumers false sense of "acting to increase safety."

It is selling of snake oil when effective medicine is available. Medical malpractice.

Pointing back to the beautiful essay on risk, and considering consumers limited resources to mitigate risk, I would conclude radon systems do a huge harm as they compete directly with mechanical ventilation.

Nice job cultivating discussion on this important topic Rodney!!

Good morning, all!

 With thanks to Mr. Fox for the heads-up on referencing the article.

 Just a quick comment regarding Mr. Lintow’s observations.


I have a readily available textbook on my shelf titled “Handbook of Noise Control” (Harris, 1957).  This classic 1,000 page textbook is as valid today, as the day Dr. Harris published the book. 


Also on my bookshelf is Rinehart’s 1943 “Mathematical Tables, Formulas and Curves” (Larson, 1943).  I reference that book several times a year. 


Also included in my standard reference library is Cadle’s “Measurement of Airborne Particles” (1947); “Pulmonary Deposition and Retention of Inhaled Particles” (Hatch and Gross, 1964); and Wells’s classic and timely “Airborne Contagion and Air Hygiene” (1955).  On a DAILY basis, I still reference my 1982 “CRC Handbook of Chemistry and Physics


Some may argue that I use these references because I’m too cheap to purchase new books every year; others may say I use them because I’m a living anachronism who is stuck in time.  But however cheap and old I may be, foolish I am not, and when I grab my 1943 Rinehart’s for reference, I so do because I know that none of the mathematical curves, roots, powers, trig operators, binomial reduction factors or indefinite integrals have changed since 1943 – no matter how pretty or expensive the latest mathematical text may look.


The “old” references used in my radon article are there for two reasons –


1) Those are the exact same articles that are being referenced in the field today and upon which virtually every publication on the subject published up to last week are based, and, the newer materials (also referenced in my article) build upon and validate the earlier references, and there is nothing there that contradicts the “older” references.


2) Like my Rinehart’s the information in them remains valid.  If you have found something in my article that is materially incorrect, and is based on an “old” reference, please provide that here and I will address it.


Regarding your comment about the increasing lung cancer rates – I have two thoughts: 1) if the lung cancer rates were actually increasing, whilst the radon programs were successfully reducing radon in homes, then this would support the already observed epidemiological evidence that lower concentrations or radon result in higher cancer rates and 2) for your reference, this morning I placed the latest SEER Delay-adjusted SEER Incidence Rates by Year which was updated May 2015 on my server here: (you can get more information regarding the graph at

In the meantime, math is still math, radiation is still radiation, and physiology is still physiology.  While civil laws may change from month to month, and societal laws seem to change daily, the laws of nature tend to resist such change.  And there is no argument to be made that old must necessarily equal invalid.


Caoimhín P. Connell

Thanks for the input Caoimhín! And welcome to this group of home performance professionals.

We are a group who are very concerned about indoor air quality for our clients, to ensure they live in a safe environment as a result of our weatherization work. Can you speak a little about your experience with balanced/unbalanced residential and/or commercial ventilation systems and how they affect Radon/CO/CO2/molds/bacteria/etc levels in a building? Specifically, are Radon mitigation systems necessary when you're exchanging enough fresh air throughout a building?

I'm also personally interested in knowing, when the science does not back the policy, how and why is it actually policy? I tend to "follow the money" when it comes to this sort of thing, but I really can't track the money in this particular case.

Hello Rodney –

Yours is a BIG question.  So, I’m going to whittle it down a bit.

As most of your colleagues already know, air has no respect for personal spaces or privacy.  

Sources of contaminants can be indoors or outdoors, and as a result, structures can act as sources or sinks for different contaminants and usually so do simultaneously.   As an example, the concentrations of ultrafine particles (UFPs) are generally two to three times greater outdoors than indoors when an healthy  structure is in “closed-mode” (windows and doors closed); reaching unity when the structure’s doors and windows are open.  Similarly, the outdoor concentrations of moulds (molds) is generally higher outdoors than indoors (contrary to what most people think this is also the case even for structures with mould problems).  As such, for these contaminants, the source is outdoors, and the UFPs and mould spores migrate indoors (the sink).

But closed conditions can also  increase the UFPs concentrations when someone inappropriately reduces the infiltration rates while placing the structure under negative pressure through the use of clothes dryers, kitchen fans, radon systems, bathroom fans, etc.

In this case, UFPs can increase through back-drafting of combustion appliances even though traditional measurement techniques (usually carbon monoxide measurements) do not reveal a problem.  (Modern offices typically operate under slight positive pressure and therefore, we don’t see these problems arising). 

In my field, we typically reference the ANSI/ASHRAE 62.1 and ANSI/ASHRAE 62.2  (both current and historical), and treat thermal loading as a “contaminant” (ANSI/ASHRAE Standard 55).  Therefore, from our perspective, “balance” is achieved when waste gases are reduced to acceptable levels and replaced with “acceptable fresh” air and potential contaminants are controlled at the source. 

With the exception of thermal loading and odors, this entire decision making processes is based on accepted toxicology.  Therefore, to your question – from our perspective, radon concentrations will virtually always be controlled to below toxicologically significant concentrations when one otherwise achieves good ventilation and a radon mitigation system is virtually never needed. 

Of course there are exceptions, I have seen houses at 10,000 pCi/l, but I am really speaking to the fact that only 2.5% of houses were above 8 pCi/l, (Nero, 1986), and yet we see people installing “mitigation systems” at levels well below even this.  That is, virtually all of the radon mitigation systems installed in the US are unnecessary and there is not a shred of evidence that the practice has reduced cancer by one iota.

Thus, it is not likely that we would ever recommend a residential radon mitigation system that affects either 1) pressure differentials in a structure, or 2) they hygric buffering capacity of the structure.   Our philosophy is that if one cannot articulate a demonstrable “problem,” then we don’t recommend “fixes” just because the guy down the street says “it’s a good idea.”

I look forward to learning from your group!


Caoimhín P. Connell


Breathtaking logic. I may not be brilliant, but I can recognize it. 

This quality of thought and expression bring tears to anybody else's eyes?

Considering there are plenty of smoke screening blower mouth's in most of these forums, finally a breath of fresh air comes out of this forum! Welcome, welcome, welcome!!! 

I don't think anyone here, much less me has an issue with old texts as much does stay the same. Unfortunately issues pop up with using incomplete information / old studies with trying to guess if the current levels are adequate, do they need to be raised or should they be lowered? Am I to take it when you say "would support the already observed epidemiological evidence that lower concentrations or radon result in higher cancer rates" that we should have more active systems / lower the threshold?

My gut call is that while one would love to believe that almost every home has a passive system, people test regularly & place an active system in when needed it isn't done except in localized areas. I would also point out that very rarely is Ted Kidd's favorite item of testing afterwards is done hardly anywhere - instead it is more like John's example - done when people move (active / passive / or none whatsoever) & only if they don't have a choice

Next on the gut call is that even if new construction has those systems, we end up tightening up many old houses without any thought of ventilation and end up making issues worse, especially when turning an unfinished basement into a finished one. That can be easily one reason why rates keep going up while smoking goes down - unfortunately without studies being done, one can't be sure & we have groups saying, oh it only causes 10%...  

As for the question on balanced ventilation - it can help &/or make things worse depending on the layout of the system, like many things it all depends.

Rodney, thanks for bringing Caoimhín's work around for another go. The guy is a true scientist, not swayed by FUD. Unfortunately that's the opposite of human nature, particularly as we are taught more and more to just be good blind followers of the bandwagon. 

I don't have much experience with the Radon thing, beyond being frustrated by it competing for limited resources against recommendations for ERV's. But to cement the bad taste in my mouth is I've never seen nor heard of installers retesting after installing. I ran across Caoimhín's work 5-6 years ago and my strong inclination is we've got a "make work" industry drilling holes in foundations and sucking air. 

Again my experience is limited, but I view any industry purporting to be "fixing" a measurable problem that doesn't measure before and after, and report outcomes to homeowners, is an industry devoid integrity or ethics. In none of my radon "mitigation" experiences was there an after test. Success was always assumed. I think if you accept "Stupid" as a defense you have a very slippery slope. 

Hmmm. Any other industry proposing outcomes and not measuring? (cough cough home performance cough cough)



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