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The Lancaster Inspector’s Corner – How Radon Testing Works

The Lancaster Inspector’s Corner – How Radon Testing Works

Welcome Back Readers!  Thanks for returning again for the second part in the Radon series from Matt Steger at WIN Home Inspection!  This week, Matt is going to tell you a about how radon testing works, so read on after the jump for that. 

Don’t forget that Matt is THE expert I recommend to all of my clients for their inspection needs, call him at 717-361-9467 so he can help you with yours! 


Last time, we started discussing what radon is and why radon is considered a serious health issue.  Let’s continue the discussion to learn what units of measure are used as well as the technologies incorporated to measure radon’s radioactivity.

What on earth is a “picoCurie”?

Radon concentrations are most commonly measured in picoCuries (pronounced peek’-o-cure-ees) per Liter of air which is abbreviated as pCi/L.  A ‘Curie’ is a unit of radiation measurement named for scientists Pierre and Marie Curie.  A “pico” is a numeric prefix meaning ‘times 10 to the negative 9th power’ or 10-9, so a picoCurie is one billionth of a Curie.  Radiation is all around us; much of it naturally occurs from sources such as outer space and inside our bodies, but also comes from many other places, such as radon and medicinal sources (like X-rays).  There is much more radiation exposure from radon and X-rays than from nuclear power plants, cosmic rays, etc.  Since breathing is the easiest way for a gas to enter the body, lung cancer is the primary result of radiation exposure from radon.

Any level of radon (and radiation) can be a health hazard, but the US EPA has compiled a considerable amount of data relating to radiation exposure and results on the body.  The EPA has chosen 4.0 pCi/L as the Recommended Action Level for radon.  If a radon test result is 4.0 pCi/L or higher, radon mitigation is recommended.  There is no radon level considered safe as even low levels may present a health hazard to certain people.  Even if a radon test shows low concentrations, simple things like remodeling a home, weather-stripping doors or windows, reglazing windows, replacing HVAC equipment, or nearby blasting can change or create new entry points of radon into the home or affect internal drafting.  In cases where one of the above is done, performing another radon test is recommended.

What is used to measure radon?

Radon concentrations can be tested using several different devices and technologies, including activated charcoal (passive), e-Perms (passive), and continuous radon monitors (active).  These are the 3 most popular testing devices used for short term (less than 90 day) radon testing.

The type of device sold in many hardware stores is an activated charcoal method tester; some professionals also use this technology.  This technology relies on radon adsorbing (not absorbing) to the perimeter surface of the individual small charcoal particles.  These devices are easily tampered with, however, so using this type of test during a real estate transaction may not be the best idea as a seller can easily move or otherwise tamper with the unit.  The charcoal test device then has to be sent overnight to a certified lab to be analyzed and the test result consists of a single radon measurement.  A delay of even 2 or 3 days between when the radon test ends and when the lab analyzes the charcoal device can void the radon test itself because radon has a 3.8 day half life meaning that after almost 4 days, the remaining radon is halved from what it was when the test ended.

Another common passive technology in use is the E-perm.  This type of measurement device relies on an electrically charged plastic membrane inside a plastic container.  After exposure, the user compares the pre-exposure membrane voltage of the charged membrane to the post-exposure charged membrane voltage.  Using a special voltage measurement tool and conversion chart, a single radon measurement result is provided.  This type of technology is temperature sensitive, so special care needs to be given when using E-perms.  Also, again since these are passive devices, they can be easily tampered with during exposure.

Another common type of technology used by radon professionals is the continuous radon monitor.  These devices are electronic and, by default, will take a measurement every hour, making them an active device.  After a standard 48 hour radon test, the licensed tester will have 48 individual pieces of data (1 piece of data per hour) as well as the average concentration for the test period.  These units contain anti-tampering technology, so if someone tries moving, unplugging, or otherwise tampering with the unit, the continuous monitor will most often indicate this information to the radon professional as well as telling what date and time the tampering event(s) occurred.  Also, if closed house conditions (we’ll discuss what these conditions are next week) are not met at the time of the radon test placement, this technology allows for the radon professional to start the test (assuming closed house conditions are now met), extend the test an extra day or so, and remove the initial 12 or 24 hours of data to ensure at least 48 hours of reliable data.  Since hourly data is provided with this technology, it also allows the radon professional to watch for patterns or other anomalies in the test data.  Since this technology stores the radon test data electronically, it can be read immediately or months later assuming the data isn’t erased or otherwise compromised.  Personally, I’ve used this technology for 5 or so years, and would not go back to passive device technology.  These units do need to be calibrated yearly, however.

Standard practice (such as during a real estate transaction) most often entails a short term radon test.  A short term test is any test lasting 90 days or less, and is most often 2 days in duration.  A long term test can last anywhere from 91 days to 365 days.  A longer test should provide a better picture of the home’s overall radon concentration over the course of several months or even up to a year, however since time is of the essence during a real estate transfer, a short term test is the most common to give a snapshot of the home’s radon concentration over the test period.

Next time, we’ll discuss the radon test requirements as stipulated by the US EPA and PA DEP.


As always, I’d like you to be part of the conversation, so if you like what you read here please comment, forward The Lancaster Connection.com to your friends, subscribe and if you have questions, need real estate advice or want to buy or sell a home, you can call or text me at 717-371-0557, email me at Jason@JasonsHomes.com or contact me at the office at 717-490-8999!

Your Friend in Real Estate,

Jason Burkholder

Weichert, Realtors – Engle & Hambright 

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Jason Burkholder