Three different methods were used to measure radon concentration in groundwater near Baia Mare andin other places of touristic interest from Maramures, the northest district of Romania. The majority ofthe samples have been measured using two methods of alpha detection. The Radon Emanometermethod has a sensibility ofl 0.074 Bq/l (2 pCi/l) and it uses a device of Russian provenience. We madeseventy (70) different measurements with this device.

There is a currently growing interest in the effect of exposure to 222Rn, because it became recognised as an important “pollutant” factor of the environment. Possible lung cancer incidence due to exposure to environmental radon levels may thus account for

Various methods to determine ²²²Rn concentration in soil gas were tested at two sites with different soil types in a depth of 1 m. They include instantaneous (spot), continuous (real time) and timeaveraging procedures with advective ('active' procedures)

Soil radon concentrations together with climatic and seismic data were continuously observed in theKanto area (Japan). During fall 1998, several typhoons and earthquakes occurred. In the meanwhile,continuous measurements of the following parameters were carried out: air pressure, temperature inthe air and in the soil, humidity in the soil, wind speeds, wind direction, rainfall and earthquakesmagnitudes.Data were analyzed using time-series analysis method, i.e. Correlation and Spectrum Analysis, so asto point out the possible relationship between radon and an environmental variable.

A test-house was realised and equipped with an Active Sub-Slab Depressurization (ASD) systemwith two suction branches. As the active element, a centrifugal fan of power 136 W was used. Thecharacteristic point of operation of the fan was determined as 370 m/h air flow rate, with -120 Papressure drop in each suction branch with respect to the atmospheric pressure. The radon activityconcentration in the sub-slab region (in gravel) was increased by means of a flow-through radongassource of 3.7 MBq activity.

A radon Test-House was realised and equipped with an Active Sub-Slab Depressurization (ASD)system to test and quantify its performance as a radon remediation measure. As active element, acentrifugal fan of power 136 W was used. The characteristic point of operation of the fan wasdetermined as 370 m/h air flow rate, with 120 Pa pressure drop in each suction branch withrespect to the atmospheric pressure. The radon activity concentration in the sub-slab region (ingravel) was artificially increased by means of a flow-through radon-gas source of 3.7 MBqactivity.

The Austrian Standard ÖNORM S 5200, prepared in the early nineties after a prestandard phase (Steger F.) and in use in Austria since 1996, provides the criteria to assess the radiation dose of building materials. Gamma radiation of the radionuclides 40K,

Radon concentration in a crawl space remained at the same level during autumn ( 756 Bq m-3 ) and inwinter ( 767 Bq m-3 ) because both air exchange rate and negative pressure (measured across thefoundation wall) increased after a installation of a new ventilation system in the crawl space. Inaddition, relative humidity and water content remained constant in the crawl space air during the sameperiod of time. Radon entry rate was explained by the pressure difference across the crawl space wallwith percentages of 51 % (winter) and 76 % (autumn).

In the study, the factors affecting concentrations of radon vertically lines were surveyed in twolarge office buildings. Integrated concentrations of radon were determined with alpha track etchfilms (2 months) and continuous monitoring (2-6 days) was carried out with Pylon AB-5equipment. The effective air exchange rates were analysed by the tracer gas method with aninfrared analyser and rates of air flows from vents were measured with a thermoanemometer.Pressure differences were measured with a manometer and temperature differences withthermoelements.

The aim of this study was to compare the measured and the calculated concentrations of indoorradon caused by building materials at 23 workplaces. The measured concentrations of radon wereclearly higher than the calculated radon concentrations from the building materials indicating thatthe main source of indoor radon was the soil under and around the buildings. The highest means ofcontinuously (933 Bq m-3) and integrated (169 Bq m-3) measured and calculated (from 70 to 169Bq m-3) concentrations of radon were found in hillside locations.