Because of the recent events at the Fukushima nuclear power plant, I got myself a Geiger-Müller counter (also known as dosimeter or radiometer).
Here’s some testing I did with it:
Background radiations are what someone normally gets since everything around us is a bit radioactive. It mostly comes from cosmic rays and terrestrial sources. The unit used is the sievert (Sv). A microsievert (μSv) is 0.000001 sieverts. A milisievert (mSv) is 0.001 Sieverts. The counter displays how many microsieverts it gets per hour, so if for example you stay near a source of 1 μSv/h during 5 hours, the total radioactive dose you’d get would be 5 μSv. In this article I’m focusing on gamma radiations.
Normal background radiations shouldn’t exceed 0.30 μSv/h.
For now I didn’t detect anything abnormal during my testing, and I hope it stays that way. These readings were taken around Geneva, Switzerland. It seems someone is doing the same as me but in Tokyo.