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RADON CONCENTRATIONS AFFECTED BY DIFFERENT FACTORS IN TWO OFFICE BUILDINGS

Raimo Halonen, Pirjo Korhonen, Pentti Kalliokoski and Helmi Kokotti
Department of Environmental Sciences, University of Kuopio
P.O.Box 1627, 70211 Kuopio, Finland

In the study, the factors affecting concentrations of radon vertically lines were surveyed in two
large office buildings. Integrated concentrations of radon were determined with alpha track etch
films (2 months) and continuous monitoring (2-6 days) was carried out with Pylon AB-5
equipment. The effective air exchange rates were analysed by the tracer gas method with an
infrared analyser and rates of air flows from vents were measured with a thermoanemometer.
Pressure differences were measured with a manometer and temperature differences with
thermoelements. Measurements were conducted during springtime 1997.
Continuously measured levels of radon varied from 17 to 129 Bq m-3. The variation of integrated
radon levels including nights and weekends was larger ranging from 20 to 350 Bq m-3. The
Finnish limit value of 400 Bq m-3 was not exceeded in any room. Correlation between
continuously measured and integrated concentrations of radon was quite high (R2=0.8125).
Concentration of radon was observed to increase if depressurisation of the room increased, the
effect was seen even on the third floor. Expectedly, radon levels were the highest in piping tunnels
nearest the soil. However, there were not essential changes in radon levels between different floors.
Radon levels correlated with air exchange rate quite good in building A (R2=0.4809) and only
slightly in building B (R2=0.0542). Theoretical concentrations of radon due to stone building
material were generally less than 50 % of measured concentrations.

Key words: radon, pressure difference, ventilation, exhalation, concrete