For many centuries, incense has been burnt for religious ceremony, therapy and to perfume the air. However, the smoke may contain toxic pollutants of respiratory health concern. This study characterised incense particulate matter (IPM) emitted from four brands of incense from Taiwan and three brands from China at different combustion stages (start, middle and end) using an Electrical Low Pressure Impactor (ELPI). Under controlled combustion conditions using a purpose-built burning chamber, the incense produced significant amounts of PM in the nanometre size fraction (0.007-0.056μm) during the whole burning time. Additional nano-sized PM was also generated in the end-stage of the combustion process. These findings suggest that PM is theoretically capable of penetrating into distal lung environments following exposure to incense smoke, with the added consequence of increased risk of respiratory injury.