This doctoral thesis describes the development and validation of a practical test procedure for the determination of the radon-222 exhalation rate from building materials under simulated indoor conditions. To ensure practical relevance, the test procedure is based on standardised and validated methods for the determination of emission of volatile organic compounds (VOC) from materials in emission test chambers [ISO 16000-9; EN 16516]. Consequently, the developed test procedure can be easily integrated into the existing global network of institutes dealing with VOC emission testing. In analogy to EN 16516, the specimen is loaded into an emission test chamber with an area to volume ratio that corresponds to the European model room. Through the test chamber, an air flow with a temperature of 23 °C and a relative humidity of 50 % is passed. For the simulation of indoor conditions, a volume flow is selected, that generates a defined air exchange rate in the range of 0.25/h to 1/h. The radon-222 activity concentration inside the emission test chamber is measured with commercial radon gas detectors, which are ideally externally connectable to the test chamber. It was shown, that measuring devices equipped with different detectors are suitable, but a minimum sensitivity was required in order to detect low building material related activity concentrations under indoor conditions of less than 20 Bq/m³ in a sufficiently short time. Due to the low activity concentrations, the determination and compensation of the background concentration in the emission test chambers as well as the device background levels were crucial. The cross-sensitivity of some detectors to the short-lived isotope radon-220 was taken into account by aging the sampled air for at least four minutes in an additional volume between the test chamber and the detector. In the validation, the test procedure proved to be robust against the variation of the test parameters product loading factor, air exchange rate, chamber volume and specific air flow rate as well as the climatic parameters temperature and relative humidity. The determination of building material-related radon-222 activity concentrations of 6 Bq/m³ to 20 Bq/m³ with a relative 1σ uncertainty of 10 % to 15 % was possible within a measurement period of a few days. Thus, the test procedure proved to be suitable for its intended use. A comparison of the developed test procedure with frequently used static test methods, where no air change rate is desired, showed partly very good matches. However, using static methods confirmed the necessity and difficulty of avoiding or accurately determining unwanted leaks of the test chamber.
Entwicklung und Validierung eines Prüfverfahrens zur Bestimmung der Radon-222-Exhalationsrate aus Bauprodukten in VOC-Emissionsprüfkammern
Development and validation of a test procedure for the determination of the radon-222 exhalation rate from building materials in VOC emission test chambers
2018
Miscellaneous
Electronic Resource
German
DDC: | 629 |
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