Characteristics of emissions of air pollutants from burning of incense in a large environmental chamber

The objective of this study was to characterize the emissions of air pollutants from incense burning in a large environmental test chamber. Air pollutants emitted from ten types of commonly used incense manufactured in different regions were compared. The target pollutants included particulate matters (PM10, PM2.5), volatile organic compounds (VOCs), carbonyls, carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides (NOx), methane (CH4) and non-methane hydrocarbon (NMHC). The particulate matters emitted from all the incense significantly exceeded the Recommended Indoor Air Quality Objectives for Office Buildings and Public Places in Hong Kong (HKIAQO). The CO peak levels of seven incense types greatly exceeded the HKIAQO standard. The formaldehyde concentrations of six types of incense were higher than the HKIAQO. The highest formaldehyde level exceeded the standard by 2 times. The results indicated that the concentrations of benzene, toluene, methyl chloride and methylene chloride significantly increased with the burning of all incense tested. In addition, the benzene concentrations of all tested incense were significantly higher than the HKIAQO standard. Although Incense 2 and 6 were claimed to be environmental friendly, the quantity of the pollutants emitted was not observed to be lower than the others. It was observed that when comparing the gas pollutant emission factors between two major incense categories (i.e. traditional and aromatic), the traditional incense (i.e. Incense 1-6) had relatively higher values than aromatic incense (i.e. Incense 7-9). Generally, it was found that the VOCs emitted sequence was aromatic incense>tradition incense>church incense (i.e. Incense 10). However, the carbonyl compounds emission sequence was traditional incense>aromatic incense>church incense. The results show that incense burning is one of the important indoor air pollution sources for PM, CO and VOCs.