It is impossible to smell, see, taste, or sense ionizing radiation. Humans have no senses for α, β, and γ rays, therefore, one has to develop detectors to replace the missing capability to see, smell, taste, or sense ionizing radiation. The necessity for the measurement of radiation exposures originates from the fact that this type of radiation has to be surveyed, controlled, and limited. Humans also have limitation to be protected against unexpected exposures. On the one hand, the of radiation exposures surveillance of radiation-exposed workers, the measurement of external radiation exposures, contaminations, and incorporations, in particular, in working areas, are very important.