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The “Reproducible Exhaust Simulator” (REXS) is a new combustion soot generator, based on the principle of a laminar diffusion flame. Soot is extracted from the stabilized flame by rapid cooling with dilution air. Due to its combustion origin, REXS soot is very similar to Diesel soot in terms of particle morphology, chemistry and size distribution, while its stability is far better than that of a Diesel engine. The soot generator can be operated against rising backpressure from a loading filter. A case study for the quality control of filter elements from mass production is presented. REXS soot is fed into filter samples, and their filtration characteristics are assesses using established nanoparticle measuring techniques. Filtration efficiency of 3 samples exceeded 99.99%, but decreased to some 99.5% for a short time after regeneration events. Leaks in the filter substrate, simulated by boring holes of 0.7 mm2 each into some end plugs, increased particle penetration 100-400 fold.