DIN ISO 11665-5:2013-06

Radon is today considered to be the main source of human exposure to natural radiation. The UNSCEAR (2006) report suggests that, at the worldwide level, radon accounts for around 52 % of global average exposure to natural radiation. The radiological impact of isotope 222 (48 %) is far more significant than isotope 220 (4 %), while isotope 219 is considered negligible. Exposure to radon and its decay products varies tremendously from one area to another. It depends firstly on the amount of radon emitted by the soil and, secondly, on the degree of containment and weather conditions in the areas where exposure takes place. This part of the DIN ISO 11665 series exclusively covers continuous measurement methods for radon-222. The standard gives indications for continuous measuring of the temporal variations of radon activity concentration in open or confined atmospheres. Continuous monitoring allows for the assessment of temporal changes in radon activity concentration in the environment, in public buildings, in homes and in work places, as a function of influence quantities such as ventilation and/or meteorological conditions. Several measurement methods meet the requirements of this standard. They are basically distinguished by the type of physical quantities and how they are detected. Examples of these physical quantities and their related detection are: - ionization current produced by several tens of thousands of ion pairs created by each alpha particle emitted by a radon that is present in the detection chamber and its decay products formed therein; - changes produced in a solid (semi-conductor medium (silicon)) by ionization from alpha particles of radon and its decay products and detected by suitable electronics. Measurement results are instantly available. A mean or integrated value can be obtained through an appropriate method based on an integration interval comparable with the phenomenon studies, but in all cases is less than or equal to one hour. The responsible committee is GUK 967.2 "Aktivitätsmessgeräte für den Strahlenschutz" ("Activity measuring instruments for radiation protection") of the DKE (German Commission for Electrical, Electronic and Information Technologies) at DIN and VDE, Joint Committee with the Radiology Standards Committee (NAR).