<p>The aim of this study was to compare particulate matter (PM) pollutants performed at three different enclosed parking garages (A, B and C) and two streets (1 and 2) in Belgium. Particle mass concentrations, number concentrations and their size distributions were measured in real time using an Electrical Low Pressure Impactor Plus (ELPI+) instrument. PM1, PM2.5 and PM10 particle ranges were characterized under this study and these concentrations were compared with the reference values recommended by the World Health Organization (WHO), United States Environmental Protection Agency (USEPA) and the European Union (EU). The results showed that the average mass concentrations in the garages ranged from 28-50 µg Nm-3 for PM1, 43-60 µg Nm-3 for PM2.5 and 58-90 µg Nm-3 for PM10, while in the streets they varied from 14-18 µg Nm-3 for PM1, 23-27 µg Nm-3 for PM2.5 and 54-59 µg Nm-3 for PM10 respectively. The number concentrations were obtained in the range of 28x103 to 47x103 particles cm-3 for the garages while 17x103 to 22x103 particlescm-3 for the streets. In all garages, it has been observed that PM2.5 concentrations exceeded the 24h reference values recommended by WHO and USEPA while and PM10 concentrations exceeded WHO and EU guidelines. Particle number size distributions showed dominant quantities of fine particles in all measurements, while two distinct particle sizes of coarse and fine modes were observed in the mass size distributions.</p>