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.
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.
Results of an investigation into factors contributing to elevated indoor radon concentrations insupposedly mitigated homes suggest that, in areas of extensive karst geological development,fluctuations in indoor radon concentrations may be extraordinary in magnitude, duration and seasonaloccurrence.
The contents of an Experimental Set are presented, providing all necessary implements for novelmethods to collect, concentrate, store and measure radon and radon decay products from harmless und ubiquitous sources of air, liquids and solids. A series of experiments is described to demonstrate the essential properties of radioactivity
Raised radon gas levels are known to exist in mines and Show Caves, and in the United Kingdomthe Ionising Radiations Regulations 1985 require the employer to take action to reduce radonlevels by improving ventilation or restricting access, because significant radiation doses can bereceived by workers.In the Mendip Hills, where the underlying rock gives rise to raised radon levels in domesticdwellings, there are a number of cave systems with unrestricted access to recreational cavers;including youth groups.
Radon gas is now considered to be a health hazard when found in excessive amounts in the builtenvironment. The levels of radon vary greatly, with some geographical areas having very highlevels. In the United Kingdom, Northamptonshire was declared an Affected Area in 1992, and itwas at this stage that our group first started studying radon levels and the steps taken to reducethem.The radon levels both before and after remediation were studied, together with the number ofoccupants of affected rooms, and their pattern of occupation.
To evaluate the dose arising from exposure to Rn Decay Products (RDP) a term often used isunattached fraction defined as the ratio of the Equilibrium Equivalent Concentration (EEC) arising from unattached radon decay products (URDP) to the total decay products, that is fu=EECu/EECt. This term is important because the large portion of the dose to the bronchial tissue per unit of inhaled activity is thought to arise due to inhalation and deposition of the URDP.
The indoor radon program in the US. started in the early 1970's in response to CongressionalHearings that recommended the initiation of radon measurements in certain parts of the united Stateswhere enhanced radon caused by contaminated uranium and radium tailings was suspect. In the mid1970's, the Department of Energy (DOE), Environmental Measurements Laboratory (EML),conducted the first indoor radon survey in the New York City Metropolitan area. The two year studyrecommended that radon surveys should be expanded throughout the US.
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