The need to measure particles in exhaust fumes from cars and engines efficiently is crucial for understanding pollution and creating measures to combat its impact on the environment. Although on-site equipment does exist to measure pollution, a more accurate, compact and real-time solution is needed to measure actual particles, regardless of fluctuating exhaust pressure. The project 'Exhaust particle number and mass measurement and sampling system' (EPONIMOS) worked on developing a compact sampling and measurement system for aerosol particles found in the exhaust of vehicles and engines. Such a novel system would not be affected by pressure build-up and pressure fluctuations in the exhaust flow. To achieve its aims, the project created a sampling technique including customised software and the necessary diluter equipment using 3D computer-aided design software. The sampling approach was then integrated with other subsystems and electronics that are pivotal for calculating and adjusting the dilution ratio, using pressure sensors, thermocouples, flow meters, throttling valves and filters. EPONIMOS subsequently tested and validated the prototype to ensure that both the hardware and software of the diluter functioned correctly. Overall, the system was successful in monitoring the particle number concentration accurately, delivering on-board measurements that were very promising. The project's results were published on the project website, EPONIMOS ,providing a host of resources for public and private use. Key findings were also disseminated through relevant conferences and journals. A pending patent application for the sampling system and final integrated system promises to ensure commercial viability of the concept. Once this is achieved, EPONIMOS outcomes will support policymakers and decision-makers across Europe in setting diesel exhaust legislation limits and applying measurement techniques.