SMALL-ION AND NANO-AEROSOL SIZE DISTRIBUTION AND CONCENTRATION PROFILE FROM CANDLE BURNING

M. D. Wright, P. A. Keitch, D. L. Henshaw

The characteristics of small-ions and aerosols produced during burning of paraffin wax tea-light candles were investigated, in the diameter range 0.4 nm to 1 ┬Ám. During burning, aerosol concentration was increased and small-ion counts were reduced to lower than background levels. After flame extinction, this trend was reversed and the number of small-ions increased to levels higher than those observed prior to burning, remaining at this elevated level for several hours. In the size distribution obtained during burning, peaks were observed at diameters 10 – 30 nm and 100 – 300 nm, consistent with ‘normal’ and ‘sooting’ burn modes. A smaller mode at diameters 2.5 – 9 nm was observed and was interpreted as the presence of a ‘soot-precursor’ species. When a fan was placed behind the burning candle a ‘modified small-ion’ signal was observed at sizes 1.1 – 2.0 nm which was not observed without the fan present, or when the fan was used with a lamp chimney shielding the flame from disturbance.

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