The text next to the image of a helicopter dropping water on a burning building reads: Dousing: Planes or helicopter are used to drop water or a fire-retardant slurry on a large fire. The slurry contains ammonium sulphate, which helps smother the fire. The text next to the image of a firefighter reads: Firefighter: Firefighters wear protective clothing, helmets, and goggles. This firefighter also carries a shovel for digging trenches to stop a fire spreading. The text next to a map showing a site of wildfire reads: Wildfire in Washington State: This satellite picture shows a forest fire that raged for two months in 2000 at the Department of Energy’s site at Hanford. The fire was started by a vehicle fire and reached more than 500 square kilometres. The labels show Boundary of Hanford site, extent of fire and smoke plume. The text next to an image of a clear strip of land reads: Firebreaks: In parts of the world where wildfires are common, strips of land are cleared of combustible vegetation to create firebreaks. Firefighters also dig firebreaks during fires to prevent fires from spreading.