In Chinese folk religion and Taoism as practiced in Taiwan, Asiatic wormwood leaves, agarwood incense sticks, and joss paper (“ghost money”) are often burned or carried to pray for health or at festivals that overlap with peak mosquito seasons. The possibility exists that some of these rituals became popular due to repellent effects of the smoke reducing the impact of insect-vectored pathogens. The effects of these smokes on the Dengue-vectoring mosquito Aedes aegypti Linnaeus, 1762 (Diptera: Culicidae) was measured following the World Health Organization guidelines for spatial repellency testing. The chemical constituents of the smoke were identified using a solid-phase microextraction fiber for extraction followed by gas chromatography–mass spectrometry. Samples are identified by the NIST library search, and checked against published Kovats Index values for a final ID. Ret. Time = Retention time. Area % - Area percentage. KI= Kovats Index.

To identify compounds in the smoke, a small amount (0.01g Artemesia, 2 cm of incense stick weighting 0.07 g, or 1 cm² joss paper weighting <0.005g) was lit to smoulder in a 10 L glass vessel covered with a layer of plastic wrap. Extraction was done using a 50/30µm divinylbenzene-carboxen-polydimethylsiloxane (DVB/CAR/PDMS) solid phase microextraction (SPME) fiber (Supelco®, Bellefonte, PA, USA) inserted into the plastic wrap to absorb the smoke for 20 minutes. The glass vessel was thoroughly washed and rinsed with methanol and acetone between repetitions and when changing test substances. The samples were analyzed using an Agilent Technologies 7890A-5975C gas chromatography mass spectrometer (GC-MS). The GC was equipped with a DB-5MSUI fused silica capillary column (30 m, 0.25 mm i.d., 0.25 μm film thickness, Agilent Technologies Inc., CA, USA). Helium was used as the carrier gas with the constant flow rate of 1.0 mL/min. The injector temperature was set at 250°C. After exposure to the smoke, the fiber was desorbed in the injector for 3 min. The GC oven settings were as follows: the initial temperature was held at 30°C for 2 min and then heated to 300°C at 10°C/min. Mass spectra were scanned in full scan mode from 50 to 500 m/z. Kovats indices were calculated based on the retention time in relation to a serious of n-alkane mixture (C7-C30) under the same analyzing conditions. The MS library identifications produced by the NIST library search were compared to published Kovats retention indices for these compounds to find matches for the Kovats indices produced by the GC.