Ultrafine particle emissions and decay rates due to burning candles in a residence

A major source of human exposure to ultrafine particles is candle use. Recent studies indicate that candles produce most of their particles in the size range under 10 nm, with perhaps half of the particles less than 5 nm. Most studies have not explored this range, having been limited to sizes >7-20 nm. In this study, emission and decay rates are estimated for three types of candles: paraffin, soy, beeswax. Number, area, and mass distributions are provided for 93 particle sizes from 2.33 nm to 64 nm. Total particle production was in the range of 10¹³ min^-1. A log-log linear relationship between decay rate (including coagulation, deposition, and air exchange rates) and particle size is found with 99% R² over this entire range. The increased particle production for the very smallest particles (2.33-2.50 nm) suggests that even smaller particles may be important to study. Results will be useful for modeling human exposure to ultrafine particles.