A method and system for treating exhaust emitted via an exhaust line from a diesel engine. A POC system is installed on the exhaust line, and has at least one diesel oxidation catalyst (DOC), a set of two or more particulate oxidation catalyst (POC) elements, a first differential pressure sensor (ΔP1) to measure the pressure difference across the first and all but the last POC elements, and a second differential pressure sensor (ΔP2) to measure pressure differences across the last POC element. During operation of the engine, ΔP1 is monitored to determine whether its POC elements require active regeneration, and ΔP2 is separately monitored to determine whether its (the last) POC element requires active regeneration.