Exploring fuel-stove and operational impacts on fugitive emissions from indoor biomass combustion.

Household air pollution (HAP) associated with solid fuel use is one major environmental factor contributing to adverse human outcomes. Although outdoor air quality influences indoor environments, severe HAP is closely and directly affected by indoor smoke leakages. However, the influences of fuel-stove characteristics and user operational behaviors on this process remain poorly understood. In this study, a suite of laboratory-controlled experiments was conducted to systematically elucidate the effects of fuel-stove characteristics and operator behaviors on smoke leakages during indoor biomass combustion. Pelletized fuels exhibited the lowest leakage fractions under the tested conditions, suggesting a better fuel-stove compatibility in terms of leakage control. Increasing chimney height from 1 m to 3 m reduced the leakage fraction of PM2.5 from 43 ± 8% to 17 ± 4%, and that of CO from 21% to 14%. User operational behaviors importantly influenced smoke leakage as closing the ash outlet reduced leakage fractions by about 24-85%, while a rapid fuel feeding increased the leakage. A generally positive correlation was observed among pollutants, however, the magnitude and dynamics of leakage differed by species. CO showed significantly lower leakage fractions than particles, and low molecular weight volatile organic compounds generally leaked less than high molecular weight species. These results indicate that leakage is strongly affected by both fuel-stove compatibility and user operation, and that assuming identical leakage fractions across pollutants may oversimplify exposure assessment and emission modeling.