Abstract: This paper investigates the smoldering of humus under different ambient temperatures to provide a scientific basis for mitigating smoldering forest fires. An experimental facility was used to conduct the fire experiments under controlled environments with temperatures stabilizing at 15, 25, 35 ℃. The mass loss rate, spread rate and mass flux of CO and CO2 were obtained and analyzed to explore the impact of ambient temperature on smoldering combustion and emissions. The experimental results showed that the smoldering of humus could be divided into three stages based on the mass loss rate: ignition, growth, and decay. Compared to 15 ℃, the peak mass loss rate of smoldering humus from an ambient temperature of 35 ℃ increased by 26.01%~29.63%. At 15 ℃, the peak smoldering temperature within 4 cm of the surface and the surface spread rate remained the slowest; the peak gas emission during the growth stage was the lowest. Within the temperature range of 15~35 ℃, the peak mass loss rate of smoldering humus increased with temperature, while there was no significant difference in the average mass loss rate during the growth stage across different temperatures. The peak CO2 mass flux during the growth stage increased with temperature, but the average mass flux decreased with temperature, no significant difference in the average CO2 mass flux during the growth stage was found across different temperatures.

Key words: smoldering forest fire, ambient temperature, spread rate, smoldering emission