What is the filtration efficiency of DPFs?
The filtration efficiency of a DPF depends upon what is measured. For whole DPM (which includes sulfates and water attached to the sulfates) the reported efficiencies for wall-flow monoliths are about 85% for cordierite and 87% for silicon carbide. Tailpipe measurements (over the MSHA certification cycle and in field DPF installations with engines loaded by torque converter stall) of elemental carbon using the same filter and analysis used in sampling for compliance has revealed reductions better than 99%. Reductions for organic carbon, in those same measurements, are somewhat less at 90 to 95%. However, the organic carbon is not sampled efficiently by the quartz filter media used in compliance sampling. Definitive field measurements of DPF filtration performance will be made by NIOSH in late spring of 2003.
