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Udvikling af sporgasmetode til brug for måling af transport af forurening mellem renserier og tilstødende lejligheder - laboratorieforsøg English SummaryThe Danish Environmental Protection Agency has initiated a project aimed to develop and test a tracer gas method that allows long-term measurements of air movements in the environment with high background concentrations of organic compounds. The method is primarily aimed at measurements in cleaning establishments and above-lying apartments. The development project is divided into three phases whereof this report describes the initial phase. The aim of the first phase is to develop and test a measurement and analysis method under laboratory conditions. If the initial phase is successful the intention is to follow-up with a number of field testing (phase 2) and measurements in existing cleaning establishments (phase 3). Laboratory experiments have been aimed at designing a method and determine a limit of detection, capacity, length of measurement period, precision, and uncertainty among other things for the method. The development work is based on the PET method for air exchange measurements developed by Statens Byggeforskningsinstitut (the Danish National Building Research Station). The project has indicated that it is possible to modify the PFT method making it applicable in situations known from the cleaning establishments where the background concentrations of organic compounds in the air are significantly higher than the tracer gas concentration. The modification consists of the following:
The chromatography and the analytical limit of detection were investigated at a number of preliminary tests with analysis of liquid standards. It turns out to be possible to detect and separate tracer gasses and cleaning fluids despite the large differences in concentrations. The analytical limit of detection is determined to be 0.03 µg (total amount per sample). The testing of the method in form of sampling and analysis was carried out by exposing the samplers to realistic concentrations of cleaning fluids and tracer gasses in a dynamic gas generation system. The tests were carried out for two sampler types (Radiello and 3M type 3500) and for two cleaning fluids (tetrachloroethylene and hydrocarbons mixtures). Perflouromethylcyclohexane (CAS no 355-02-2) and perflouro-1,3-dimethylcyclohexane (CAS no 335-27-3) were applied as tracer gasses. The compounds are often mentioned by name of PP2 and PP3 respectively. The concordance between the theoretical and experimental determined uptake-rates is more than 80% improved with a single exception for the 3M samplers. The theoretical determined value is calculated from tracer gasses' diffusion coefficients in air. This is assessed to be satisfactory and within the expected compared to other investigations of experimentally identified and calculated values. The experimentally identified uptake-rates for the two samplers appear from the report and should be used at prospective use of the method. The relative standard deviation for the specific uptake-rates is in the order of 10%. The project has indicated that the method's capacity allows measurements for up to fourteen days without the sampler displaying any signs of saturation. With tracer gas concentrations of 15 µg/m3 in the cleaning establishment the method's limit of detection will be able to detect concentration reductions of up to a factor 1000 in the above-lying apartments at measurements exceeding fourteen days. An assessment of health risks at the projected tracer gas concentrations has been carried out. The assessment has been carried out based on existing data sheets and information in a number of reference works and databases. The Danish Environmental Protection Agency's has supplemented with a toxicological assessment of the tracer compounds. The effected assessments indicate that a concentration of 15 µg/m3 hardly poses a risk for the people on the premises. No conditions assessed to be critical to the continued development of the method have been detected during this phase. The second phase of the project – implementation of a number of field tests – can therefore be initiated. In connection with the implemented laboratory tests circumstances that should be included and clarified during the coming phase have turned up. It is concerning an assessment of possible sink effects significance for tracer compounds. Coming phases should also include Rynex cleaning establishments in the testing of the method.
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