Background

Air quality modelling of smoke from wildfires requires knowledge of emission factors and how these vary.

Aims

Experimental fires were used to test the variation of emission factors with fuel load to improve a smoke forecasting model.

Methods

Gas and particle-phase chemical composition of smoke plumes from laboratory-scale fires was measured with different fuel loads and at different stages of fire progression.

Key results

Different fine woody debris loads had no significant effect on the emission factors. In contrast, different stages of the fire produced significant differences in emission factors. The lowest emission factors for most species (except carbon dioxide) were observed during the flaming fire front, which accounted for half the total emissions. Importantly, we found that emission ratios relative to carbon monoxide were consistent across different fuel loads and throughout the fire’s progression.

Conclusions

By modelling the modified combustion efficiency, it is possible to simultaneously model the emissions of carbon monoxide and the emissions of nearly all other pollutants throughout the progression of a fire.

Implications

The emissions of carbon monoxide, fine particulate matter and other key pollutants all scale with the intensity of the fire, simplifying the task of modelling these emitted pollutants downwind of prescribed fires.