Small-ion and nano-aerosol production during candle burning: Size distribution and concentration profile with time

The characteristics of small-ions and aerosols in the diameter range 0.4 nm to 1.1 μm, produced during burning of paraffin wax tea-light candles, were investigated using a custom-built aspiration condenser ion mobility spectrometer (ACIMS) and a sequential mobility particle sizer and counter (SMPS+C) system. Peaks in the number concentration were observed at diameters 10–30 nm and 100–300 nm, consistent with “normal” and “sooting” burn modes. In addition, a smaller mode in the size range 2.5–9 nm was observed, interpreted as a soot-precursor species. When a fan was placed behind the burning candle a “modified small-ion” signal was seen at sizes 1.1–2.0 nm. This was not observed without the fan present or when a lamp chimney was used. During burning, aerosol concentration was elevated and small-ion counts were low. However after extinction of the flame, this trend was reversed and the number of small-ions increased to levels higher than those observed prior to burning, remaining so for several hours.