Environment and radon measurement by gamma spectrometry

The protection of the environment against ionizing radiation is today a vital necessity, given the multiple risks to which are exposed mankind and other living creatures.Risks could arise from natural radiation (radium, uranium) or artificial (tests of nuclear weapons, industrial facilities using the atom to pacific ends). Among natural sources of radiation that may draw radioactive contamination risks, the author gives the example of Radon (222Rn).He tries to answer to some questions: why do we measure radon? how do we measure radon? how much is the significant quantity of radon? what kind of measurement system can we use?etc (N.K.)