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  • Writer's pictureCameron Home Inspections

Radon: What is it and How Much is Too Much?!

Updated: Aug 29, 2022

Radon often comes up during real estate transactions and is one of the most common inspection requests I receive - and for good reason! This blog post will discuss what radon is and why it's so dangerous, where it comes from, how it typically enters a house, how it's measured, and common mitigation procedures.

Radon is a an inert gas formed by the naturally occurring radioactive decay of uranium which is found in the soil and rocks below us. Radon is found throughout the world in various concentrations, but it cannot be seen, smelled, or tasted. Without the use of specialized detecting equipment, radon remains invisible. Some geographic areas may have more or less radon, but it can be measured everywhere.

As uranium decays, it produces a handful of Radon Decay Products, or RDPs. Some of these RDPs emit alpha particles as they continue through their decay cycle. While alpha particles typically cannot even penetrate the skin, they can easily be inhaled. Once lodged in delicate lung tissue, the particles continue to emit radiation which can damage the lung cells and can cause cancer. In fact, the Environmental Protection Agency estimates that radon is the second leading cause of lung cancer behind smoking and is responsible for about 21,000 lung cancer deaths every year! The Centers for Disease Control and Prevention (CDC), World Health Organization (WHO), American Lung Association (ALA), and American Cancer Society (ACS) all have similar warnings about the dangers associated with this invisible gas.

Because it is found in the bedrock and soil beneath us, radon will naturally come in contact with a home's foundation. That said, all the radon we measure doesn't just happen to float into house from below - some of it certainly will seep through even the smallest cracks and pores in a foundation...but a phenomenon known as stack effect is what's most responsible for increased indoor radon concentrations. Air is effectively sucked into the home from below to replace that which has escaped out of the roof above. Vents, whole house fans, heating and cooling equipment, and even wind can all increase radon levels inside due to how they create pressure differentials and facilitate air movement.

Radon concentrations can vary by season and are impacted by weather events like heavy rain. Typically, the highest radon measurements will be found during the winter months due to increased stack effect or when the soil is particularly wet or frozen. Winter measurements will usually yield the highest results, but a winter measurement doesn't always fit into your home buying or selling schedule. Long term tests (90 days to a year) are available and may be prudent to know exactly how your radon concentrations fluctuate over an extended period and with the seasons...but that doesn't do much in the meantime if you're closing on your home purchase or sale in a week or two!

The EPA's Home Buyer's and Seller's Guide to Radon sheds much more light on the short term test (48 hours) used for real estate transactions as well as the action level where radon mitigation is recommended. According to the Agency, 1 out of 15 homes across the country have radon levels that should be mitigated! The Montana Department of Environmental Quality also has some great information about radon - and they also suggest testing during all real estate transactions, even if a passive or active mitigation system is installed. It's no wonder...the majority of Montana falls within the EPA's Zone 1, meaning most homes that have not been properly mitigated are predicted to have an indoor radon concentration above the EPA's Action Level...we'll discuss that in detail shortly.

When I perform a short term radon test, I use a Continuous Radon Monitor (CRM) - this method allows me to download the test data and produce a detailed report like this one immediately upon completion of the 48 hour measurement. The ease and accuracy of a CRM allows me to confidently report measured radon levels quickly, and meets nationally-required parameters for testing as part of a real estate transaction.

Now that you've seen a radon report, you probably noticed the measurements labeled in pCi/l, or picocuries per liter of air. No level of radon is considered safe, but the EPA has placed the Action Level at 4 pCi/L. Even below this level, the EPA still recommends periodic retesting. Home owners or buyers who receive a report with measurements between 2-4 pCi/L should consider mitigation, especially if the test was conducted when radon levels are typically not at their highest.

Mitigation systems vary both in function and cost, but the most common is called active subslab suction (also known as subslab depressurization). In this system, a pipe (usually PVC) is installed directly below the basement floor or in the crawl space and extends up and out of the house. A motor and fan is connected to the pipe which sucks the air directly from below the house and exhausts it outdoors where any radon dissipates safely in the atmosphere. For this system to be effective, the fan must continuously run. A properly installed mitigation system can decrease even the highest indoor radon concentrations, but should be installed by a qualified contractor and independently tested to ensure it functions as designed. Passive systems including a vapor barrier and similar piping also exist, and are common in new construction.

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I hope this post has helped you better understand all about radon...where it originates, how it gets inside, why it's dangerous, and how we measure and mitigate it. If you found the information useful, please share it with a friend and as always, call, text, or email at any time with questions or to schedule your radon measurement! Don't want to miss future blog posts? Click here and subscribe at the bottom of the page! -Jon ASHI #265859 406-306-1331

*The views and opinions expressed in this blog are those of the author and do not necessarily reflect the official policy or position of any other agency, organization, employer or company.

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