Team observes new soot-free fire 'blue whirl'
US-based researchers have discovered a new type of fire, "blue whirl", that evolves from a fire whirl and burns with nearly soot-free combustion. Soot includes fine black particles, composed of carbon produced by incomplete fuel combustion. "Blue in the whirl indicates there is enough oxygen for complete combustion, which means less or no soot, and... cleaner burn", a researcher said.