The National Institute for Nuclear, Biological, and Chemical Protection, under the European project 16ENV10 MetroRADON (the European metrology program for innovation and research, EMPIR), has developed unique equipment for the testing of measuring devices at low-level radon activity concentrations. The equipment consists particularly of an airtight low-level radon chamber (LLRCH) with an inner volume of 324 liters; a Rn-222 type RF 5 flow-through source with a Ra-226 activity of 4.955 kBq developed by Czech Metrological Institute within the above-mentioned project; and a pressure vessel as a radon-free air source. The mass flow controller of the Bronkhorst EL-Flow type is a part of the apparatus and ensures the requested airflow through the radon source—partialized if necessary—through the chamber. The homogeneity of the atmosphere in the chamber is ensured by means of a continuously regulated fan (airflows in the range of 0.1–3.5 m·s⁻¹ can be established). Another important chamber component is the measuring device of climatic conditions, since temperature, air pressure, and relative humidity must be determined. The construction of the equipment allows the time-stable radon activity concentration to be maintained at a precise level for several days. Radon concentration values can be arbitrarily and continuously set in the range from 100 Bq·m⁻³ to 300 Bq·m⁻³.

An interlaboratory comparison for European radon calibration facilities was conducted to evaluate the establishment of a harmonized quality level for the activity concentration of radon in air and to demonstrate the performance of the facilities when calibrating measurement instruments for radon. Fifteen calibration facilities from 13 different European countries participated. They represented different levels in the metrological hierarchy: national metrology institutes and designated institutes, national authorities for radiation protection and participants from universities. The interlaboratory comparison was conducted by the German Federal Office for Radiation Protection (BfS) and took place from 2018 to 2020. Participants were requested to measure radon in atmospheres of their own facilities according to their own procedures and requirements for metrological traceability. A measurement device with suitable properties was used to determine the comparison values. The results of the comparison showed that the radon activity concentrations that were determined by European calibration facilities complying with metrological traceability requirements were consistent with each other and had common mean values. The deviations from these values were normally distributed. The range of variation of the common mean value was a measure of the degree of agreement between the participants. For exposures above 1000 Bq/m³, the variation was about 4% for a level of confidence of approximately 95% $\left(k=2\right)$. For lower exposure levels, the variation increased to about 6%.

Knowledge of the active size distribution of radon daughters is one of the main parameters for determining the effective dose from inhalation of short-term radon decay products. However, this parameter is crucial for accurately determining an effective dose; there are currently very limited possibilities for determining it. This paper describes the laboratory validation of a method for determining the activity size distribution of radon decay products using the Dekati ELPI+ cascade impactor and the Graded Screen Array Diffusion Battery (GSA DB). Using nuclear track detectors placed on individual impaction plates of the cascade impactor, the equivalent equilibrium activity concentration of individual size classes can be determined in the range from 17 nm to 10 μm. A diffusion battery was used to detect smaller particles in the unattached fraction area. The presented method can further refine the knowledge of the activity size distribution of radon decay products in different types of workplace atmospheres. Workplaces with higher radon concentrations differ significantly in the size distribution of aerosol particles, radon activity concentration, and equilibrium equivalent activity concentration.

An international comparison of continuous monitors measuring radon activity concentration was performed to validate the traceability of the European radon calibration facilities. It was carried out by comparing the secondary standards used by these previous facilities, ranging from 100 Bq·m⁻³ to 300 Bq·m⁻³. Secondary standards were individually compared to a secondary reference device previously calibrated in a reference radon atmosphere traceable to a primary standard. The intercomparison was organized by the National Institute for Nuclear, Chemical, and Biological Protection (SUJCHBO) in the period from October 2019 to April 2020 within the European Metrology Program for Innovation and Research (EMPIR), JRP-Contract 16ENV10 MetroRADON. Eight European laboratories participated in this study. The results of the experiment are presented and discussed.

Inhalation of radon and its short-lived progeny is one of the most significant contributors to the total effective dose from natural sources of ionising radiation. Exposure to radon progeny represents a substantial health risk, primarily due to its established link to lung cancer. Dose coefficients are derived from biokinetic models describing the behaviour of radon decay products in the respiratory tract, combined with dosimetric models that account for energy deposition from emitted radiation. Given the variability of environmental and working conditions at different workplaces, obtaining site-specific aerosol data to support more accurate and tailored dose coefficient calculations is beneficial. The key parameters influencing effective dose include the equilibrium equivalent activity concentration (EEAC), total aerosol concentration, and the size distribution of radioactive aerosol particles. Additional factors such as work activity, relative humidity, and ventilation type significantly affect aerosol characteristics and, consequently, the equilibrium factor (F) and the unattached fraction (f_p), which can vary considerably between sites. This study presents field measurements of the activity size distribution of short-lived radon progeny at several workplaces, using the Dekati ELPI + cascade impactor and the Graded Screen Array Diffusion Battery (GSA DB). The measurements were conducted primarily at underground workplaces with natural ventilation, including former mining excavations and tourist caves. For comparison, the study also includes one site with forced ventilation-a facility for disposing of low-level radioactive waste-and one outdoor location influenced by radon exhalation from a uranium mining waste rock dump.

This paper focuses on the issue of non-financial corporate reporting by the Czech chemical companies. Based on the content analysis of the websites and disclosures, it analyses, compares and evaluates the level of web communication of the economic, environmental and social issues of corporate social responsibility of these companies. At first, it presents results of the research comparing the extent of non-financial web communication of selected Czech chemical companies with the Czech leaders in the Czech TOP 100 rankings. These results are then complemented by results of the quantitative research on environmental instruments used by all Czech chemical production companies, that use websites for communication of their activities. The number of companies in the Czech Republic processing non-financial reports is significantly lower than abroad, but it is still growing. Large enterprises pay more attention to non-financial reporting. Rather than including this information in a disclosure, a business website is used as a tool for this communication. The paper brings sectoral perspective into non-financial reporting literature, as attention is paid to the chemical production sector and also complements the knowledge of communication of companies that do not belong to the group of 100 most important companies within the country.