Coupled effects of ignition technique, chimney draught, and air supply on emissions from residential combustion

Residential wood combustion emissions are strongly influenced by user operation and installation-dependent parameters, yet the combined effects of ignition technique, chimney draught, and air supply remain insufficiently characterised. This study evaluates the coupled impact of three ignition techniques (top-down, bottom-up 1, bottom-up 2), two draught regimes (natural and forced), and the presence or absence of under-grate air supply on gaseous (CO, OGC, NOx) and particulate (TSP) emissions from a closed fireplace insert burning beech logs. Across the full combustion cycle, CO emissions ranged from 2355 to 3554 mg Nm −3 and OGC from 290 to 865 mg Nm −3 , depending on draught and air supply regime. Under natural draught without under-grate air supply, CO concentrations reached 3554 ± 320 mg Nm −3 (top-down), whereas forced draught with air supply reduced CO to as low as 2355 ± 225 mg Nm −3 (bottom-up 1). Under-grate air supply consistently decreased CO and OGC emissions under both draught regimes, with OGC reductions particularly pronounced for top-down ignition under forced draught (290 ± 50 mg Nm −3 ). Fuel-bed arrangement influenced emission performance. In the absence of under-grate air, bottom-up 2 generally produced lower CO and OGC emissions than bottom-up 1, demonstrating that not only ignition direction but also wood arrangement affects combustion dynamics. NOx emissions showed limited variability (90–107 mg Nm −3 ) and increased slightly with under-grate air supply. TSP emissions ranged from 83 to 135 mg Nm −3 , with no statistically significant trends across ignition techniques or draught conditions. Under-grate air supply was the most consistent factor reducing gaseous emissions.