Like the catalytic converter, the diesel particulate filter consists of a ceramic substrate, with a high degree of porosity. It also has a cell structure, but in this case with the cell inlets or outlets blocked alternately; in other words, when the inlet is blocked in one cell, the output is obstructed in the adjacent cells.
This means the exhaust gases have to pass through the porous walls of the filter, where the particles are retained.
Depending on the ceramic material used in the manufacture of the substrate, the filters are either cordierite or silicon carbide. The cordierite filters are lighter, simpler to manufacture and cheaper; while silicon carbide filters have better physical features and last longer.