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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An item of concern is that getting cancer has everything to do with breathing in some molecules and they get embedded anywhere next to a cell can be in your mouth not just the lungs, then part of the gut.

Like other low-level radiation reducing the concentration changes the odds but doesn't remove the risk.

Thanks, from an abjectly ignorant non-scientist's view the question that is 'begged' is this. Does the alpha radiation from the bananas, wine, beer, etc. decay into potentially damaging charged particles?

Good morning, Mr. Cullen –

As I mentioned in another post – for the purposes under discussion on this site, alpha particles don’t decay; alpha particles are the product of a decay – thus alpha particles from the Am241 in your home smoke detectors don’t decay, alpha particles from radon 222 don’t decay, the alpha particles from the radon daughter polonium 218 don’t decay and alpha particles emitted from bananas, beer, bicycles or milk don’t decay.

The question: “Does the alpha radiation from the bananas, wine, beer, etc. decay into potentially damaging charged particles?”

Can be simplified to: “Does alpha radiation decay into potentially damaging charged particles?”

To which, the simple answer is ”No.”

We are awash in a sea of radiation in and around our bodies, the beta from the K40 found in virtually every cell of our body , the C14, N13, N15, and O15 we breath every second and so forth. 

Every second, some 2E18 high energy protons (1E9 eV)  are incident on the earth. A single high-energy proton may give rise to hundreds of millions of secondary particles including electrons, muons, photons and so forth.  If one is worried about a measly PAEC of 4 pCi/l then for heaven sakes don’t get on that airplane this summer to visit Grandma – the average dose rate for folks in the US from cosmic and terrestrial radiation is less than 0.1 microsieverts (µSv)/hr. But that airplane you are sitting on at 35 000 feet, the dose rate from cosmic radiation alone may be between 3 and 9 µSv/hr (depending on your latitude, the higher numbers at higher latitudes and the lower exposures as one gets closer to the equator).  In fact, commercial airline pilots are exposed to more radiation on an annual basis than nuclear plant workers.

Worrying about residential radon is rather like setting up a camping tent on a railroad track frequented by freight trains, and then spending the night awake worrying if you remembered to take your daily vitamin. 

As Bernie Cohen once stated with exasperation in a Letter to the Editor Nature Magazine in the mid 1980’s “Why pick on radon?” 

Why indeed, and Cohen used the entire body of science to pose the question – and I will follow the science wither it goes. 



Good morning, Tom –

You raise two very good points: 

Risk is a number, and that number is never “zero.”  Risk is merely a probability of an occurrence.  As such, each human in the US and Canada have a risk (probability) of 1E-7 of not living through this day.  That is, the total combined causes of death (crime, motor vehicle accidents, disease, age, etc) means that any randomly selected human has a 1 in 10 million chance of dying today.  Now, 1E-7 is a small number (0.0000001), but it is not “zero.”  As such, there is never anything as “no risk.” 

Consider the probability (risk) of getting hit by a meteor – it was reported that 1,000 people were injured on Feb. 15, 2013 around Chelyabinsk, Russia when a 7,000 ton meteor exploded on entry.  Although I have not double checked the reference, it is reported that Phil Plait (a.k.a., “The Bad Astronomer”) calculated a risk of getting hit by a meteor was 1 in 700,000 (which is 1.4E-6)… again a small number but not zero.  Now could you reduce the risk even further by wearing a steel hat and armor plate whenever you go outside?   Could you reduce the risk even further by never going outside? Could you reduce the risk even further by living 4km deep within the Mponeng gold mine?  Of course you could – but why would you, just to reduce the risk of getting hit.

Whereas risk is objective, then the number is low enough, we encounter a subjective threshold called “safety.”    That is, “safety” is the attainment of an acceptable level of risk.  Risk is objective, and safety is the irrational acceptance of a specified level of risk. 

So, when someone wants to install a “radon mitigation system” to avoid the measly 225mrem/year of radiation, I would pose to them the following question:  “Just how safe do you want to be?”  And why, then, if you are worried about radon in your home, are you willing to drive to the grocery store and get milk (which carries five times more risk of death than radon in a home).  Or indeed, why are you willing to live in South Carolina, instead of Tennessee, since living in SC carries ten times more risk of death than living in Tennessee.  Why are you going to spend $2K dollars installing a radon mitigation system in your home, but you are doing nothing about removing the ambient benzene form your home, that carries far greater risk of cancer than does radon?  What about the 100 mrem you are about to receive by flying out to California to see your great Aunt  Agatha? 

The answer lies in “fear.”  People don’t fear driving to the store, because it’s a familiar risk – even though every one of us has driven by numerous horrific motor vehicle accidents (MVA), and each of us has personally seen the blood and guts and death, and probably personally know someone who has been killed in a MVA, yet probably none of us has see someone who was killed by radon – Similarly, one chooses to live in South Carolina or Georgia because those are nice places, and the fact that living in those states versus living in Nebraska, or Oklahoma increases the risk of death ten times greater than radon never enters people’s minds.  Why?  Answer: Awareness.  The general public has been unnecessarily frightened out of their wits with irresponsible statements from various government entities wherein the risks are neither put into perspective and are not based on science. 

If 4 pCi/l of PAEC (radon) results in a significant risk because a radioactive disintegration may occur at a cellular level, then consider this:  If you are an average US adult, you have about 150 grams of potassium in your body right now. As you sit and read this post, you are irradiating about 4,400 Bq (120,000 pCi) of just the K40, (that equates to about 4,400 radioactive disintegrations per second).  And that’s just from the potassium! And that occurs in your body each second you live.)   At least 98 % of those disintegrations take place within body cells, and are potentially capable of altering the cell's DNA.  So why aren’t you dead from cancer – indeed, why didn’t you die from cancer before the age of 2?  Our own bodies irradiate us with ionizing radiation, at a rate of one fifth of that the average US citizen receives from radon (when we express the exposure as “dose” in mrems per year).

Answer – because, as of today, February 3, 2016, there has not been a single valid study ever performed on the face of the earth, devoid of confounders and unsupportable assumptions that has ever shown with confidence that radon, as typically encountered in homes increases the risk by an single iota.  Indeed, most of the legitimate epidemiological studies performed thus far, show that the cancer rates in homes with low levels of radon are LOWER than the cancer rates in homes with no detectable levels of radon.   To be clear, the majority of legitimate studies show that, at levels typically encountered in homes, as the radon concentrations go up, cancer rates go DOWN. 

However, whether this is a statistical anomaly or not, I don’t care because either way, we are dealing with risks that are vanishingly small, and entirely insignificant, even if they are real. 

So, as I sit here in my office in Bailey, Colorado, writing this post, I think of the poor souls in Denver where the cosmic radiation pours down some 2,000,000,000,000,000,000 high energy protons (each greater than one billion eVs) every second, and are receiving about 0.02 mrem every HOUR!  Do I gasp at the fact that my office is at 9,000 feet elevation where my hourly dose may be as high as 0.04 mrem/hour?  No. I don’t gasp – Indeed, later today, I will drive about 125 miles which will swamp the risk of NORMs in my environment.  That’s risky.  Indeed in my case, I also happen to be part-time police officer, and  so later today I will don a ballistic vest, holster a gun and face the world as it presents itself to me.  Should I worry about radon as I drive around in a marked patrol car?   Probably not; currently I am much more concerned about the spider on the ceiling directly above me – now THAT’s frightening! But am I "safe"?



Caoimhín P. Connell


Utterly fascinating. Thank you for taking the time to write all this! As I work on my Home Performance book, a link to this thread is going in the IAQ chapter.

A follow up question. If a ceiling fan helps reduce exposure, how about turning the HVAC air handler on continuous and moving the air around the house all the time? Is that likely to help as well?

Typical AH fans are 3/4 hp.  1725 watts to 1 HP so 1293 watts.  1293x24x365 = 11,326 KWH for the year. Subtract regular usage assume 50% time so 5663 KWH.  FTC uses 12.7 cents per KWH as a national rate for those yellow energy guide labels on appliances  so 719.24 per year to run fan. 

Fan Tech HP 190 Radon Mitigation Fan is rated at 69 watts.

Fan Tech ERV 704 80 watts

Exhaust Only ventilation use Broan Nutone Bath fan 55 watts

You can figure the difference for your self.  IMHO the cost is significant for operating cost increase.

Screen shot of Infinity Control

John, take a look at that link. This is a Carrier GreenSpeed heat pump on a very moderate day, about 50 degrees outside. 70 indoors. 1820 cfm leakage in a 1600 sf house. I have the fan set to continuous low with an ECM fan. This is the first data point with any continuous fan showing because the heat pump ran so little the fan actually had to run on its own. It used 1 kWh in 24 hours. $.11. Even if you attribute the whole 8 kWh to the fan, it's $1/day. That house is the most comfortable one I've ever been in by an order of magnitude. Sadly, no fresh air system yet... my other GreenSpeed project does have an HRV.

Another reason not to use crappy equipment with PSC fans... your math could be correct for them.

John, you would prefer use modeled from rating over actual measured use?

Ted  You always start with independent data. That is necessarily not actual but lab tested.  Then you move to a model.  Then you take actual usage and compare to the model.  Then you find the reasons for atypical deviation from the model.

BTW:  I could have used Carrier nech data  2.3 fan amps at 220 VAC.  Same difference.

I could just kiss you, Caoimhín ;) You've really gone above and beyond in your detailed explanations about this subject of Radon, presenting fact over hype. Hopefully we folks who call ourselves "building scientists" can assimilate this science into our daily practice. Thanks for everything!

Agreed. We really need a like button. 

I just asked Diane, the moderator of this website for that "feature request". Let's see...


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