PM10, PM2.5 and PM1 mass concentrations have been measured at Delhi (28°35'N; 77°12'E) during the August to December 2007. The running mean of PM10, PM2.5 and PM1 data shows large variations. The PM10, PM2.5 and PM1 were ranged from 20 to 180 μg/m3 during the monsoon and from 100 to 500 μg/m3 during the winter (up to 1200 μg/m3 in November due to Deepavali fireworks). For the same running mean cycles, higher mass concentrations in the PM10, PM2.5 and PM1 were corresponded with peaks in the relative humidity and lower levels linked to peaks in the ambient temperature. The evolutions of PM10, PM2.5 and PM1 concentrations after the elapsed times are simulated with mean mass scavenging coefficients. These evolution patterns clearly show the difference in washout of PM10 with impaction scavenging relative to those for PM2.5 and PM1 particles over different rainfall durations. Air-mass pathways traced with HYSPLIT model over the study area illustrates the nature of PM10, PM2.5 and PM1 levels with monsoon and winter air-mass circulations over Delhi.