[en] Experiments have been conducted with 0.61x0.61m commercially available HEPA (High Efficiency Particulate Air) filters to determine how air flow resistance varies with collected particulate mass. Combustion of the two organic fuels, polystyrene (PS) and polymethylemethacrylate (PMMA), at high and low burning rate conditions generated the combustion aerosol for plugging the filters. Results indicate that the resistance ratio, (actual filter resistance/initial filter resistance) correlates the filter mass gain for PS and PMMA by the function given. Experiments were also done to determine the material depletion due to deposition on duct walls. The aerodynamic particle size distribution and particulate mass concentrations were determined by cascade impactors. Since PS and PMMA represent extremes of smoke producing materials found in a nuclear fuel recycle facility, the results obtained for the filter coefficients should bracket those expected in accidental fires at recycle facilities. (author)