Frame-by-frame analysis of the motion of individual sootparticles then reveals how quickly gases within the fire are moving, and allows fire behaviour to be scrutinised in detail.
First, when released into the air as a result of incomplete combustion (from sources as varied as badly serviced diesel engines and forest fires), sootparticles absorb sunlight, and so warm up the atmosphere.
Campaigners worry that incinerators produce dioxins (a highly toxic family of chemicals that can cause cancer and birth defects) and tiny particles of soot (also carcinogenic).