EPA test Protocols – “Protocols for Radon and Radon Decay Product Measurements in Homes” by the EPA has been the guiding document for radon testing for many years. But at 47 pages, it’s rarely read. We edited it to 4 pages that Realtors and home inspectors should commit to memory.
Short term testing – A short term test runs 2 to 90 days, depending on the device. All short term testers will give you a very accurate reading, but only of a short window of time. Although the radon levels in most homes will vary by perhaps 10% to 20% depending on the weather and the season, a small number of homes will have significant variations. So if you have time, it’s usually best to do a long term test.
Long term testing – A long term test runs 3 to 12 months, and gives the best picture of your real radon exposure. Many people start with a short term test, and if the results are marginal, follow up with a long term test.
Test types – Continuous electronic monitors are usually requested by home buyers because they are very hard to tamper with. They must be operated by trained professionals.
Charcoal tests are the most common form of testing because they are cheap, accurate and simple enough for anyone to do. Most people place two units side by side in their basement. Minnesota residents can order discount priced charcoal tests from Aircheck.
Alpha track is the most common long term tester. It is also very simple. It is best to deploy it over multiple seasons, with some heating, some cooling and some open windows. Minnesota residents can order discount priced alpha tracks from Aircheck.
E-Perms are reusable and are usually deployed by public health departments. They can be used short or long term.
Homeowner testing – All tests
• Put the test unit in the lowest level of the home that is regularly used.
• Put the test unit away from drafts, high heat, direct sun and high humidity.
• Put the test unit 2’ to 7’ from the floor, at least 1’ from exterior walls, at least 3’ from exterior doors or windows and at least 4” from other objects.
• Do not put the test unit in kitchens, bathrooms, laundry rooms, furnace rooms, closets, porches or crawl spaces.
• Do not put the test unit near sump holes or floor drains.
• Do not test during severe storms, if winds exceed 30 mph or if the barometric pressure is rapidly changing.
• Except for normal traffic, keep doors and windows closed for 12 hours before the test and during the test.
• Do not use whole house fans or fireplaces.
• Room air conditioners must recirculate the room air, not exhaust it .
• The furnace, central air and air exchanger (HRV) should be running normally.
Home sale testing
• A professional tester should apply tamper detecting strips to basement doors and windows and tell the occupants what they can and can’t do during the test.
• Follow the same guidelines as for home owner testing, except the test unit should be put in the lowest level that has a concrete floor and could be finished.
• For charcoal tests, the EPA requires the use of 2 units in the same location, either simultaneously or sequentially.
What if the house was vacant during the test?
A typical home changes its entire volume of air through natural leakage every 2 or 3 hours, whether it’s occupied or not. As air leaves the home, up to 20% of the replacement air comes in from underground- bringing in radon. If you could seal the house above ground and stop air from leaving, you would also stop the underground air and the radon that comes with it.
So assume you had a house with a radon level of 10pCi/L, and you sealed the house above ground. Radon stops coming in. Radon has a half –life (the time it takes a radioactive element to decay into half of what it used to be) of just 3.8 days, so in 3.8 days you will have 5 pCi/L. 3.8 days later it will be 2.5, 3.8 days later it will be 1.25, etc. Soon, the “sealed up” house has virtually no radon. Then, un-seal the house so that it starts leaking again, and within a couple hours the radon will be back up to its normal level.
But this is really a moot issue, since it’s not possible to seal a house airtight. Locking the door and leaving the home unattended for a month has certainly not made the home air tight.
Just to add to the confusion- studies imply that if you reduce a home’s air leakage by 90%, you will reduce the radon entry by 90%. But since the fresh air that normally leaks into the home and dilutes the radon has been reduced by 90%, the radon level remains mostly unchanged. Conversely, if you open some upstairs windows and increase the home’s air leakage by 90%, you will increase the radon entry by 90%. But since you have increased the fresh air in the home by 90%, the radon is diluted and the overall radon level remains mostly unchanged.
But- these comments are generalities and a gross oversimplification of a complex process, and every home will behave with its own idiosyncrasies.