Medium-Term Radon Testing is a compromise between the relative rapidity of Short-Term Testing and the much more reliable Long-Term Testing.
The length of time of a Medium-Term Radon Test is between 1 month and 6 months. That’s the amount of time that Radon detectors would have to be on-site.
However, setup times are similar to all other radon testing options, so radon testing and measuring technicians won’t be on-site for longer than an hour or so. The exact time depends on a possible, prior, exploratory radon inspection or visit that would reduce the setup time.
The stronger reliability of a Medium-Term Testing is proportional to the duration, as all radon tests, but a Medium-Term Test can span across one or two seasons.
Since there is generally a marked difference between seasons, a Medium-Term Test can show highs and/or lows, and generally a significant variation of Radon presence. It could be enough to determine a trend and grossly calculate the annual variation without having to wait for a year long test.
However, Radon can change significantly at any moment, so Medium-Testing just doesn’t quite give the peace of mind that a Long-Term test can offer.
In conclusion, the usual rule applies, the longer the testing and monitoring for radon, the better.