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Physical characterisation of $$\hbox {PM}_{2.5}$$ PM2.5 , $$\hbox {PM}_{10}$$ PM10 and surface ozone measured during the period from 17 July to 21 August 2012 at four strategic locations in and around the Lumbini Protected Zone, Nepal, is done to assess air quality of the region and understand qualitatively source mechanisms of these pollutants. The measurement locations are Panditarama Lumbini International Vipassana Meditation Centre, Parsahawa, Bhairahawa and Tilaurakot, representing monastic, industrial, urban and control areas, respectively. The overall average concentration of $$\hbox {PM}_{2.5}$$ PM2.5 at these locations is $${\sim }19\pm 12$$ ∼19±12 , $$35\pm 13$$ 35±13 , $$35\pm 11$$ 35±11 and $$25\pm 6~ \upmu \hbox {g/m}^{3}$$ 25±6μg/m3 and of $$\hbox {PM}_{10}$$ PM10 is $${\sim }25\pm 11$$ ∼25±11 , $$103\pm 41$$ 103±41 , $$58\pm 15$$ 58±15 and $$32\pm 7~ \upmu \hbox {g/m}^{3}$$ 32±7μg/m3 , respectively. $$\hbox {PM}_{2.5}$$ PM2.5 never crosses the safe limit of the National Ambient Air Quality Standards of Nepal (NNAAQS) in the monastic and control areas but either crosses the NNAAQS occasionally or remains in its vicinity at the other two locations. The $$\hbox {PM}_{10}$$ PM10 concentration frequently exceeds the safe limit in the industrial area but not in the other remaining areas. The analysis indicates the dominance of the impact of local sources and boundary layer thickness on the atmospheric loadings of the particulate matter. The daily average mixing ratio of surface ozone remains normally low at all the four observational sites although the mixing ratio of ozone at Panditarama Lumbini International Vipassana Meditation Centre is much lower than the NNAAQS but higher than that observed at Tilaurakot.