Customer Review: The documentation I got with my house showed a radon reading above 50.0 before a mitigation system was installed and < 4.0 after it was installed.
The radon mitigation fan broke and I falsely thought painting / sealing the basement floor (years ago) would stop the radon.
After plugging in this unit I got a reading (after a few days) around 10.0 and it went up day by day. I replaced the mitigation fan when the reading was around 20.0. This unit then showed the level go down each day (took about 2 weeks to get to safe level).
Highly recommend this considering you can spend $15.00 a pop on those radon testers you mail in. One I used said I had a safe level.