n. An agglomeration of small carbon particles in smoke.
Small carbon particles in smoke agglomerate to form a larger soot particle. Soot is evidence of fuel-rich combustion. Within the context of wildland fire, it is high-temperature soot and ash particles that make the visible flame, and lower-temperature soot particles that produce thick black smoke. Soot can be quantified by particle number density (in other words, the number of particles per unit volume) and the distribution of particle sizes; however, these parameters are difficult to measure because soot particles continually change in size and shape as they are lofted through the fire plume over time.