The new German Radiation Protection Act (StrlSchG) of 31 December 2018 established a reference value of 300 Bq m−3 for the annual average radon activity concentration in buildings with recreation and living rooms, as well as in workplaces. It is expected that the reference value will be exceeded in a vast number of buildings throughout Germany and that radon protection measures will become indispensable. A simple and inexpensive radon protection measure for existing buildings is ventilation. In the scope of a joint project, ventilation systems with zone control and heat recovery are to be extended by the control parameter radon activity concentration. A highly sensitive, miniaturized radon monitor will be developed for this purpose, which can be integrated wirelessly into ventilation systems. Radon measurements were carried out in 13 apartments of an unoccupied heated apartment block in Germany over a period of three weeks in the wintertime. High radon activity concentrations were found on all three floors. The maximum values were 14000 Bq m−3 on the first floor, 6000 Bq m−3 on the second floor, and 2000 Bq m−3 on the third floor. Ventilation experiments were carried out in an apartment with high radon activity concentration. Two decentralized ventilation systems with heat recovery were installed in each of the two opposite outside walls. The controlling device of the system was activated wirelessly depending on the radon activity concentration. The radon activity concentration was reduced from 8000 Bq m−3 to 800 Bq m−3 in a first experiment in the living room.

No abstract

<p>Since new radon risk maps for Germany were published in 2021, in Saxony the highest spatial accumulation of precautionary areas can be found. Reasons are the geological subsoil like the Ore Mountains, as well as a historical mining industry and intensive uranium mining from 1946 to 1990.</p><p>Close to a heap, various ventilation experiments for indoor radon reduction were performed in a two-room flat (ground floor) in Bad Schlema (Germany). As an innovative approach to eliminate indoor radon and prevent new radon from entering, the focus is on creating an over pressure within the flat. This developed ventilation mode, which aims to ensure that more fresh air enters the room than leaves it, is called differential pressure mode with a forced over pressure.</p><p>Therefore, a decentralised ventilation system with heat-recovery from inVENTer (Germany) was installed. Throughout numerous different ventilation experiments, radon activity concentrations [Rn] were continuously measured in all rooms (including basement and balcony) using Radon Scout Plus devices from SARAD (Germany). Thereby, room-specific radon behaviour with and without ventilation was found.</p><p>Despite a strong seasonal trend with significantly higher indoor radon levels in Sep.-Nov. and Dec.-Feb. than in June-Aug., an overall reduction of indoor radon of up to 80 % was achieved. Important to mention is that different ventilation modes in combination with different fan performance levels resulted in different indoor radon reductions.</p><p>Here, in particular, the experiments with forced over pressure (up to +5 Pa) led to significant results in summer and winter, even in rooms with higher [Rn]. For example, measured [Rn] of 7.000 Bq/m<sup>3</sup> within the kitchen could be reduced to 300 Bq/m<sup>3</sup> and maintained for the entire duration of the respective ventilation experiment.</p><p>In this work, the performed experiments as well as the room-specific ventilation effect will be presented. Furthermore, this work analyses the dependencies between the reduction of indoor radon activity concentration and the corresponding environmental parameters.</p>

No abstract