grab samples were obtained before and
after burning(0.5 h after the incense has extinguished).
The samples during burning were time-integrated
samples, drawn at a flow rate of 38.08–79.57 ml min1
(depending on the burning time of the incense) using
mass flow controllers (model FC4101CV-G, Auto flow
Inc., CA). After sampling, the samples were analyzed
within 3 h. Prior to sampling, sequential evacuating and
pressurizing with humidified zero air was used to clean
the canisters. 10% blank sample canisters filled with
standard gas containing target organic compounds of
known concentrations were conducted during sample
collection and storage with other sampling canisters for
GC/MS analysis. Prior to the experiments, background
air samples were collected to ensure the background
levels do not exceed 10 mgm3 of TVOC and 2 mgm3 of
many individual VOC. Detailed description of the
analysis can be found in Lee et al. (2002). A total of
38 VOCs species were identified by the GC/MSD system
and 11 species were selected in this study.