Characterization of Fine Particle Emissions from Burning Church Candles

Abstract

A series of source tests were conducted on the combustion of paraffin and beeswax candles. An enclosed chamber sampling system was utilized, and fine particle samples were collected on both quartz fiber and Teflon filters. Electronic particle sizing was performed using an optical particle counter and a differential mobility analyzer. Filter samples were weighed to determine fine particle mass emission rates and then analyzed for elemental carbon and organic carbon by thermal evolution and combustion analysis and for organic chemical composition by GC/MS. Three modes of candle burning were observed with very different emission profiles:  a “normal burning” mode characterized by low mass emission rates and particles smaller than 100 nm in diameter; a “sooting” behavior with high emission rates of predominantly elemental carbon particles; and a “smoldering” phase upon candle extinction during which most of the mass emissions occurred as white particles having diameters between 400 and 800 nm. The majority of emissions were organic compounds including alkanes, alkenes, alkanoic acids, wax esters, cyclohexylalkanes, and alkanals. Analysis of the unburned waxes revealed that while some of these compounds were thermally altered products of the unburned wax, many others were unaltered candle components emitted by direct volatilization. Thus, possible chemical tracers for candle burning may be easily identified by analyzing unburned wax material. The information provided in this study, in conjunction with future ambient indoor air sampling programs and receptor-oriented chemical mass balance techniques, can be used to determine the relative importance of candle burning to indoor soiling problems.