artificial dissipation of fogs, usually by seeding or heating. It is done primarily at airports to improve visibility. Many attempts have been made to clear fogs at temperatures above freezing by seeding them with salt particles and by heating them with burners, but these techniques remain undependable. Fog dispersal at temperatures below freezing, however, is regularly performed at many airports by seeding them with solid carbon dioxide or with propane gas sprayed from the ground. Compare cloud seeding.