Agricultural chemicals are frequently applied by spray from aircraft, specially designed spraying vehicles or by hand from backpacks. In more built-up areas pesticides are sprayed on parks, school playing fields, footpaths, roadsides, pavements and public buildings. Spray application is also used for domestic weedkillers and wood preservatives. Spraydrift or mist is invisible clouds of small droplets of the chemicals which it is claimed are carried on the wind even across oceans.