A passive particulate filter is a standard, ceramic honeycomb structure with alternate plugged channels. A catalyst is typically upstream of the filter but may be integrated into it. In certain cases, a washcoat layer of catalytic material may be placed on the filter in addition to the catalyst.

Passive particulate filter systems rely exclusively on chemistry to regenerate. As carbon moves through the exhaust, it is trapped by the particulate filter. That filter begins to build up with carbon and other residual exhaust species, which have also become trapped. This will continue until conditions become favorable for the elements to internally combust off the filter surface. The heat for this regeneration comes from the thermal energy that occurs naturally with exhaust temperatures of typical diesel engines.