Fig 1 (a) cross-section view, front view at (b) depth=0 and (c) 150 μm, and (d) back view of a 9th stage nozzle of the MOUDI; (e) cross-section view, front view at (f) depth=0 and (g) 120 μm, and (h) back view of a 9th stage nozzle of the NMCI. (Dashed circles demarcate the circumferences of the step or holes) (Liu et al., 2013).

Fig 3 Micrograph of the 7th to 10th [(a) to (d)] stage nozzles of the MOUDI and the 7th to 10th [(e) to (h)] stage nozzles of the NMCI after incense smoke sampling (Liu et al. 2013).

Fig 2 Particle collection efficiency curves of the 7the10th stages of the MOUDI and NMCI. And ambient aerosol mass size distributions measured.

Fig 4 Micrograph of 9th stage nozzles of the (a) NMCI and that of the (b) MOUDI before ultra-sonication. Micrograph 9th stage nozzles of the (c) NMCI (for 1-hr) and that of the (d) MOUDI (for 1-min) after ultra-sonication (400 W, 40 kHz).