Radon is the leading cause of lung cancer in the U.S. among non-smokers and 1 in 4 homes in and around Portland has high radon. Unfortunately, radon levels are not static over time. Let's look at why you should retest every 1-3 years.
Radon levels under the home can change over time. Radon is trapped in the soils and slowly released beneath the home. The Pacific Northwest has earthquakes that could open pockets of radon gas or provide new pathways for it to get to your home. In fact, earthquakes happen multiple times a year in our area. Click here to see the number of earthquakes in Oregon over the past year.
The way you live in your home affects radon levels. If you (homeowners) leave windows open or go in and out a lot during a radon test the radon levels in the home will be lower because the outdoor air coming in has almost no radon. In contrast, If you leave the home closed up, radon levels will be higher. This difference can change concentrations by 5X. If the radon was tested while someone else lived in the home, retesting with a year long test is recommended.
Radon levels change over the year. If you had a radon test when buying a home you have a snapshot of the radon levels (typically 2-4 days). The stack affect, which causes warmer air inside the home to rise and pull more radon into the home, is far greater in the winter when outdoor air is much cooler than indoor air. This means radon levels tend to be greater in the winter than the summer. Long term testing eliminates the short term fluctuations.
Atmospheric pressure can affect short term radon testing. We installed atmospheric pressure sensors on all of our radon machines for a year to see if pressure affected radon levels. We know the stack affect changes radon levels which would mean atmospheric pressure would too. And, it did. Every time there was a quick drop in atmospheric pressure radon levels would increase and when the pressure increased for 24 hours radon levels would decrease. When pressure drops it creates a suction that pulls more radon gas into the home and less when pressure increased. Long term testing will not be affected by short term changes in pressure.
Changes to the home can alter radon levels. These include a new heater, adding an A/C, remodeling, finishing basements or even adding fans in the bathrooms or kitchen. All of these changes impacts the stack affect and can alter radon levels. Anytime significant changes are made to the home retesting is recommended.
Short term tests are great at telling you what's happening over the short term but it's the long term that really matters. A one year test is going to be more accurate than a snapshot 2-4 day, 1 month or even 6 month test. We recommend retesting with a year long test.
Why do we do short term testing?
Short term testing is all there is time for in real estate transactions. It gives you a good idea of what to expect throughout the year so you can make decisions before purchasing a home.
Can I do long term radon testing myself? Yes.
Note: the digital testing equipment below has not passed the AARST-NRPP certifications and cannot be used for real estate transactions. Here are a couple of options for DIY long term radon tests.