I have been looking for an answer about what a Geiger counter actually measures. I am puzzled by the claim that it can actually give measures in sieverts/hour, i.e, measure the dose equivalent received by the body. On Wikipedia (Geiger counter article), I read: "a G-M tube can detect the presence of radiation, but not its energy which also influences the radiation's ionising effect. Consequently, dose rate measurement requires the use of an energy compensated G-M tube, so that the dose displayed relates to the counts detected. The electronics will apply known factors to make this conversion, which is specific to each instrument and is determined by design and calibration." Obviously, the device cannot know that I am in a cellar full a Radon inhaling alpha-emitters, which is obviously much worse than walking on a field of beta-emitters. Furthermore, if "a G-M tube can detect the presence of radiation, but not its energy", it should mean that the result should be in becquerels (number of desintegration per second) and not grays (J/kg). Everytime I read that some people live in a place with, let's say, 1,000,000 Bq/m², I wonder how many sieverts it might be yearly for the inhabitants and I always think it is impossible to calculate that, because it depends on the quantity of dust inhaled, the water they drink, the food they eat, the kind of houses they live in. Now super little Geigers seem to be able to provide this tricky conversion automatically! Waoo!!