Spray driers turn liquid foods into powders, for example liquid milk into dried milk, by spray drying. The liquid is atomized into a fine mist inside a hot-air chamber, where the droplets dehydrate almost instantly, and the solids fall to the bottom of the chamber as dry powders for collection. They are the workhorses behind milk powder, whey powder, infant formula base, and instant coffee production. Design and operation demand attention to hygiene, since the warm, moist zones of a drier can harbour microbes, and to powder properties such as particle size, bulk density, and instant solubility.