Development of a radiochemical test procedure for the separation of aerosol-borne allergens

Abstract

An innovative radiochemical method has been developed to determine the filtration efficiency of HEPA filters for biological nanoparticles. The setup based on EN 1822, for flat sheet media, is up to 40 times more sensitive for a single particle than methods based on particle counting, even for low particle concentrations. To achieve such a high sensitivity the radioactive tracer technique is utilised using a solution of bovine serum albumin (BSA) labelled with radioactive iodine (131I). With the aid of an aerosol generator, this solution is nebulised into nanoparticles of a defined size, which are then passed to the test filter via a compressed air flow. On the raw and clean gas side of the test filter, the 131I is measured with two NaI(Tl) detectors. By balancing the measurement data with each other, the filter efficiency can be determined. Initially, the setup has been validated with current particle counting methods, according to EN 1822, to ensure its functionality. Subsequently, the first experiments with radiolabelled nanoparticles gave promising results, as will be shown below. Further experiments also yielded information about filter clogging and its influence on the filter efficiency.