I made this chart. Several other blogs have copied it nearly verbatim, and I am happy that others want to spread actionable information to protect people (would have been nice to get a proper credit though). I had the chart translated to Japanese as I was sending a Geiger to Japan to help families address their real risk. See bottom for the Japanese version.
This is a super condensed table on how to interpret Geiger Readings. Use it to supplement your own research and getting a "block of knowledge".
If you take this radiation stuff at all seriously, then get a Geiger. All the rest is guesswork.
Radiation Alert Inspector, $530 to $600 Amazon
And Here are LIVE radiation reports from independent reporting stations.
I am sending my Radiation Alert Inspector to Japan to a family that needs real data---soooo You won't see an Oahu based reporting station until I get my next Geiger delivered.
Japan –only 2 to 5 reporting sites