The rise in air pollution in Europe is a pressing environmental health concern, and road transport is a major contributor. To address this issue and meet new emission standards, exhaust aftertreatment systems must be improved. Understanding the composition, properties, and amount of particulate matter (PM) produced by diesel engines is critical for reducing PM emissions with the diesel particulate filter (DPF). This research provides an in-depth analysis of PM emissions produced by heavy-duty diesel engines, with focus on understanding the sources of PM emissions, their impact on the structure and on the reactivity of the PM. Various filters to collect the particulate were employed and critically analysed.