The four types of incense were placed in a chamber with a relative humidity of 40 ± 5% for 24 hour before sampling. The weight difference before and after sampling was the total weight of incense burning. Before sampling, a 37-mmquartz
filter (Pall 2500 QAT-UP) was conditioned in a high-temperature environment at 900 C for 4 h to remove carbon and thereby prevent the interferenceof overly highcarboncontent