Modelling ventilation system operation in order to reduce natural radiation in buildings

Over 70% of the total annual radiation dose received by the human population comes from natural sources of radiation; 40% of that quantity is due to the presence of the natural radioactive gas, radon. Its most common and most significant isotope is radon-222 (²²²Rn). Indoor radiation activity occurs due to radon migration from soil and due to other radioactive substances present in building materials. The most important factor that influences indoor radiation activity concentration is ventilation. It is very important to optimise the concentration of indoor radiation activity and ventilation system intensity for human health, environment and energy saving, because earlier studies paid scant attention to the issue of radon concentration decrease by ventilation. The software Resrad-Build is used to simulate exposure to radiation of persons working or living in a building contaminated with radioactive material, in the case of a typical basement and a room above the basement. The model evaluated the maximum length of time between two automatic activations of the ventilation system and the minimum value of the permanent ventilation intensity needed to make the average annual received radiation dose for the person less than 1 mSv.