We report on a study of particle emissions from pulse-jet cleaned filter media and filter ageing effects of up to 10,000 cycles, which were obtained in laboratory tests on a VDI test rig, using two measurement systems adapted specifically to determine size selective data according to PM2.5. Time resolved measurements were made with an optical counter recalibrated (for the test dusts Pural SB and NF) to directly read dust mass vs. aerodynamic diameter according to the PM2.5 transmission curve. In parallel, a cyclone was used as pre-separator in combination with an analytical filter to obtained emitted dust mass averaged over a number of cycles.
Regarding PM2.5 emission levels, one can draw different conclusions from the same data, depending whether total emissions per cycle or average concentrations per cycle are reported. The results also illustrate how ageing depends on the type of dust and the duration of ageing cycles. Ageing progressed more rapidly with the coarse, free flowing dust. The 5 s ageing cycles prescribed by VDI and ASTM protocols are too short.