Radon Measurement FAQs - American Radon Mitigation

Radon Measurement FAQs

Radon testing can be confusing. What’s the best way to test? How do you interpret the results? We sat down with Bruce Snead, Director of Engineering Extension at Kansas State University, to answer common radon measurement questions. Bruce has worked in the radon industry since 1988, doing training, outreach, technical assistance, and working with states in the industry. KSU has had a radon chamber since 2018 and provides national technical assistance for the EPA, answering five hotlines and selling short-term and long-term test kits. The transcript has been edited for length and clarity.

Jesse: Is blank level of radon safe? 

Bruce: There’s no safe level of radon. It’s a source of naturally-occurring radiation, and we want to minimize our exposure to it as much as reasonably achievable. There’s radon indoors; that’s where it accumulates. There’s radon outdoors, but it’s very low. So radon is everywhere; testing is the only way to know the level. And we want to minimize our exposure. That’s why the surgeon general recommends that all homes get tested for radon. When homes are found to be 4 pCi/L or more, mitigation is recommended. So there’s no quote “safe” level of radon. There’s going to be radon that we have to learn to live with. But with testing and mitigation, we can keep it low.

J: So the lower, the better?

B: Lower, the better.

J: What does the EPA action level mean, and why is it 4 if they recommend mitigating above 2?

B: Right. The EPA action level was based on work to fix houses built on uranium mine tailings. So it’s a technical guideline, not a health-based guideline. And that’s why the guidance says if you get results between 2 and 4, consider fixing. If you get 4 or more, it’s recommended to mitigate the structure. The guideline is not a standard, but it functions as a standard in real estate transactions. It’s what everyone relates to.

It’s also a personal decision in terms of what you’re willing to accept exposure to. I’ve had people say, “I want to get the radon level down below 1.” That’s a significant effort with mitigation to achieve that. It can be done, but anything below 2 is an excellent mitigation result, and you have to decide. Because it’s naturally occurring, it’s not regulated, so it’s a negotiable item in a real estate transaction. But ideally, we want to minimize it. The 4 pCi/L guideline is relatively conservative when we compare it to other international standards. So I think it’s a sound basis for negotiating this item in real estate transactions. 

J: Where does that guideline come from? Why is it 4?

B: It’s because of the work done to mitigate homes built on uranium mine tailings in the Grand Junction, Colorado area. That’s where it comes from. Experience and what they could get the houses down to. So that’s become the national guideline. And it’s, you know, it could be 5, it could be 3, but it’s 4, so that’s what we have to live with. 

J: Okay, thank you, because that’s a question I’ve always had.

J: Our next question is, “Why do radon levels tend to be higher in the winter?” 

B: In terms of heating-dominated climates, the northern half of the United States is probably dominated by heating more than cooling. And in the winter time, the temperature differential between the indoors and the outdoors, say 65, 70 degrees indoors and 0, 20, 30, 40 degrees outdoors, creates a stack effect. And that stack effect means warm air indoors rises and can draw in radon from the soil. So we find that in heating-dominated climates, winter conditions may be the ones that create the highest indoor radon concentrations because of this stack effect pulling the radon from the soil into the home. 

J: Our next question is, “What conditions impact radon fluctuation, and how much fluctuation is normal?” 

B: Radon is a fluctuating phenomenon. It doesn’t just stay one number and remain that way. It fluctuates because of a variety of factors and forces. Air pressure differences caused by the stack effect that I mentioned. Warm air rising in the home. The wind effect pushing and pulling on buildings. The venting and combustion of appliances in the home. As well, the circulation caused by heating, ventilating, air conditioning systems in the home. All of these things, coupled with weather and soil conditions, affect radon concentrations, so they commonly fluctuate in a home. If you look at 48 hours, 96 hours, 4 days, 5 days, and 6 days, you’ll see a fluctuation.

Let’s say the average is 3; it might fluctuate between 1 and 6. If the average is 10, it might fluctuate between 5 and 15. Those are typical ranges of fluctuations that you might see. And radon tends to have a diurnal pattern as well. That’s why we test for a minimum of 2 days when we do short-term tests, so we get a good average that averages out those fluctuations. 

Radon Fluctuations

J: The next question is, “How accurate are radon test kits or tests?” So like charcoal test kits versus digital monitors versus professional tests. 

B: Okay. All the devices that are approved for professional service, for use by folks like Jesse in conducting tests in the real world, are listed with the National Radon Proficiency Program. To be a listed device for use by professionals means that five of those devices were exposed to a range of high, medium, and low radon concentrations, relative ranges of temperature, and relative humidity. And all five devices were exposed five times to different parameters, and all had to be within plus or minus 25% of the radon concentration each time to achieve a listed or approved status. So that’s the criteria and evaluation that a device has to go through to achieve the listed status. And all of the devices you’ll see on that website, activated charcoal canisters, pouches, you know, most of the devices that are available for purchase publicly are that now.

There is another group of devices called electronic digital monitors. These are consumer digital monitors. They tend to cost much less than professional-grade monitors that cost $600 to 4,000. So there are consumer monitors that have not gone through that evaluation, that typically cost $125 to $350, something like that. And those devices, while good for consumers are not a basis for a mitigation decision by a professional. So it’s a little bit confusing. And it’s good that we have these consumer devices because more testing gets done. People want to know their radon concentrations more frequently than one short-term test every season or once every two years. So they’re good devices, and they help folks be aware of radon levels. But they haven’t gone through a rigorous evaluation in terms of their performance. 

J: So our next question is, “What’s the difference between a DIY test and a professional test? When would you use a professional test?” 

B: Well, anytime you’re in a real estate transaction, you should use a professionally-based test. This might be done with different devices that the professional is qualified to use. We recommend everyone test their own home. A do-it-yourself test, purchasing a test kit online from many of the suppliers that are available, or checking your state radon program and perhaps your county extension office to see if they have low-cost or sometimes even free test kits you can use.  

So test your own home. It’s always good to do that. Go through the process. But anytime you want to make a decision about whether or not mitigation is warranted, it’s great to contract with a professional so that you get a result that you can rely on. Do-it-yourself tests are more subject to user error than a professional who conducts the test with knowledge about the protocols and standards so that the test is a reliable basis for decision-making about mitigation. 

J: Our next question we might’ve kind of already answered. What’s the difference between a consumer digital monitor and a professional one that a professional would use? 

B: The professionals are more expensive. Usually, they have the capacity to download data on an hourly basis. A number of consumer digital monitors do not have that. They can’t download the data. All you can do is punch a button and see the number. Some of them have the ability to share hourly information, so it depends. And we’re seeing a lot of improvements with software and Bluetooth connections so that we can learn more about radon levels from these devices, but that’s primarily the difference. A professional device has gone through an evaluation program and proven its performance, whereas consumer monitors have not gone through that evaluation.  

J: Why do I need to have a post-mitigation test if my digital monitor says my radon levels are low? 

B: Well, it’s because certified mitigation professionals have a standard to perform to, and that includes assuring that a post-mitigation test is done. They’re going to want to do their own test to verify their own system effectiveness. But they must recommend an independent test. The homeowner can test their own home if that’s an approach they want to take, or they can recommend an independent measurement professional conduct the test. But we want to verify that the system is working. While a consumer digital monitor is a reasonable way to look at that, we want to make sure we have an independent verification through a proper test. 

J: Alright. And our last question, “Should I worry about radon in my water, and how would I test for that? Test or treat that?” 

B: Sure. Well, radon in water is a much less significant problem than radon in air. In fact, if your home is served by a private well, it’s possible that the water that comes out of the well into the home and is used for showering, bathing, washing, and all the things that we use water for domestic purposes for, may release radon from that water into the air. And obviously, different rates and volumes of use would release different amounts of radon into the air, but that’s a secondary source of radon in a home. The primary source is the gas that comes out of the soil underneath our foundations through gaps and cracks because of the vacuums and suction that the house and various driving forces exert on the house.

Where to Start

So you always test the air in your home first, and if you find high levels, take steps to reduce it. If it still remains high, there’ll probably be some other evaluation of the mitigation system to be sure it’s working. Radon water tests may be appropriate if you are in areas that have been identified as having radon in water problems.  

If it’s found to be high, and radon in water levels tends to be tens of thousands of picocuries per liter if we’re going to warrant mitigation. It takes 10,000 picocuries per liter of radon in water used in the home to produce an average of about one picocurie per liter of radon in air. It takes a lot of source to contribute significant levels to the home. But, if you find elevated radon in the water, there are two options.

Water Filtration

One is called filtration. Radon in water can be filtered out by running that water through a carbon filtration system. This is only suitable for a certain amount of radon in water levels, and it is a filter that will ultimately require servicing and replacement. 

Water Aeration

Another, more efficient approach is what’s called aeration. In an aeration system, the water is brought into a box and then aerated inside an enclosed box with shower heads, drip irrigation, or other means to stir and air the water out and strip the radon out of the water. Then suction is exerted with a fan on that box, extracts the radon, and dumps it into the air outside. So it works similarly to a common soil mitigation system, except here we’re sucking the radon out of the box where the water has been aerated to strip the radon out and make it airborne so it can be vented to the outside.

This is a more expensive process, and the problem is not as widespread. There are areas of the country where it’s much more common to have radon in water problems. I would suggest that folks go to their state radon program to see if they have any guidance about radon levels in the water that may be applicable, especially in the northeastern United States.

For more resources regarding radon measurement, visit sosradon.org 

Contact us to schedule a professional radon test or an estimate for mitigation.