The effects of air staging and combustion air control on black carbon and other particulate and gaseous emissions from a sauna stove

The combustion of wood in small-scale appliances emits significant amounts of particulate and gaseous pollutants into the atmosphere, leading to impaired air quality and adverse health and climate effects. Simple and easily implemented reduction techniques are needed to address this issue. In this study, different air staging strategies in a sauna stove were investigated with high temporal resolution, and the relationships between combustion air settings, combustion parameters, and different emission components were examined. Air staging was found to decrease PM1 and BC emissions by 43 and 41 %, and CO and OGC emissions by 23 and 42 %, respectively, when the stove was used in its standard configuration. Reducing and redistributing primary air decreased emissions further. BC emissions were lowest when the sauna stove was operated with an air-to-fuel ratio of 1.5. BC correlated weakly with gaseous emissions, with the exception of acetylene, highlighting the role of C2H2 as a precursor gas in soot formation. High OC/EC ratios during experiments with inefficient combustion conditions led to high average AAE values, which ranged from 1.23 to 1.41. Instantaneous AAE values correlated with concentrations of carbonyl compounds, especially acetaldehyde, suggesting that carbonyls may be indicative of BrC in wood smoke. The results show that significant emission reductions can be achieved in a simple combustion device with small, easily implemented modifications. In addition, the highly time-resolved data revealed relationships between various emission components, combustion conditions and the formation and properties of soot.