The measurement of 222Rn is based on the interaction of ionizing radiation with matter. Measuring devices offered by are characterized by the following measuring principles:
- ionization in a silicon semiconductor detector
- scintillation in zinc sulfide ("Lucas cell")
- generation of tracks in plastic material
All mentioned interactions are triggered by alpha radiation due to the radioactive decay of 222Rn (energy of the alpha particle energy: 5,49 MeV), 218Po (6,00 MeV) and 214Po (7,69 MeV). Only 222Rn is allowed to get into the measuring chamber and to the detector, radon decay products have to be retained by air filters or the casing itself. Inside the measuring chamber, 222Rn decays and the radon progeny contributes to the result of the measurement.