At the same location the radioactive snow fell in Arkansas the air filter was reading very high at 246cpm. Higher than a smoke detector that is listed as hazardous waste.
One thing noted is this level is effected by humidity. High humidity gives a lower reading. So this detector is most likely reading a daughter product of something else. Many will say radon, I am assuming because the get paid to do so. However, the fact remains it is only a guess.. the filter has to be tested to be sure. Anyone checking there own air filters should do this during low humidity. Is the area covered in some kind of hard to detect meltdown fallout? It's impossible to know without a much more intense investigation by a lab or maybe a $15000 detector that can measure the energy level of that radiation. Just be careful changing your own air filters, odds are this is not a local event to just White County Arkansas.