...As an expert on radiation effects, and a research career that spans over 35 years, I can assert that Radon detectors (and the level set as "safe" by the EPA) are pseudo-science.
The human body contains enough potassium-40 (a radioactive isotope) to register more than 4 pCi! So far as I know, the K-40 in our bodies has never been linked to an increased rate of cancer. One only need sit or sleep beside one of the detectors for most of the "collection" period to register positive for Radon.
Meanwhile, how can a gas which is much, much heavier than air "rise" up through a home? Heck, Radon is even heavier than ALL commonly occurring metals, including Gold! It can only FALL out of the cracks in basement walls (if those walls contain or are near a high concentration of Uranium), where any Radon will turn to Lead within a few weeks. It must constantly be "replenished" by some source (that source is Uranium).
If you had a true Radon problem in your basement, you'd also have a problem with Lead on your basement floor, and Uranium in-or-behind your basement walls. There's no need for a Radon detector at all, and ventilation systems will do almost NOTHING to mitigate any problem with Radon -- it is too heavy to ventilate.
The entire Radon mitigation industry is a scam perpetrated by environmental activists pushing an agenda to grow the power of the federal government to control our environment, and who are ignorant about physical science.
Cancer is "linked" to a great number of factors using statistics. When I studied advanced probability & statistics, I was taught that figures don't lie, but that liars do it with figures. This is the case for "Radon"-induced cancer.
The EPA justifies the Radon scam by claiming that up to 21,000 people die annually from Radon-related lung cancer.
The problem is, the EPA's study failed to separate... wait for it... smokers from non-smokers.
Of course, anyone with an ounce of sense would ask: why do I have to spend $1,000 to "fix" a problem that no one can see, that no one can smell, has never hurt a single person, and apparently didn't exist until 1984?
Oh, right. It's for the children.