A three-staged cascade virtual impactor was designed, fabricated, and used as aerosol classifier in a dust sensor module. The dust sensor module consisted of the impactor, three commercial dust sensors, and four pumps. For the design of the impactor, three cut-off diameters of 2.5 ㎛, 2.0 ㎛, and 1.5 ㎛ were selected. Then three nozzle widths were determined from computational fluid dynamics (CFD) simulation with the three designed cut-off diameters. </br>Laboratory generated PM2.5 aerosols classified into each of three sizes, via the fabricated impactor, entered a dust sensor from which voltage signals were detected due to particle scattering by a laser diode in the sensor. The voltage signal data from the three sensors were converted to number concentrations of the dust particles utilizing correlation equations obtained from separately performed experiments. The number concentrations were in agreement with those obtained by aerodynamic particle sizer (APS).

Atmospheric aerosol particles were investigated at GNTECH university in Jinju city. Samples were collected using the Nanosampler period from January to December 2014. The Nanosampler is a 6 stage cascade impactor(1 stage : > 10 μm, 2 stage : 2.5~10 μm, 3 stage : 1.0~2.5 μm, 4 stage : 0.5~1.0 μm, 5 stage : 0.1~0.5 μm, back-up : < 0.1 μm) with the stages having 50% cut-off ranging from 0.1 to 10 μm in aerodynamic diameter. The mass size distribution of Atmospheric aerosol particles was unimodal with peak at 1.0~2.5 μm or 0.5~1.0 μm. The annual average concentrations of TSP, PM10, PM2.5, PM1, PM0.5 and PM0.1 were 44.0 μg/m3, 40.3 μg/m3, 31.4 μg/m3, 18.0 μ g/m3, 8.2 μg/m3, 3.0 μg/m3, respectively. On average PM10, PM2.5, PM1, PM0.5 and PM0.1 make up 0.91, 0.70, 0.41, 0.19 and 0.07 of TSP, respectively. The annual average of PM2.5/PM10 ratio was 0.77.