Applying compressed air foam, the total water supply (total gallons) required to extinguish a fire is reduced to as little as one-third compared with applying water alone. This also carries through to exposure protection. Compressed-air foam clings well to vertical fire exposures, which means less water is wasted from runoff during exposure-protection operations. In rural areas where water supplies are scarce, if exposure-protection applications are needed, more water remains available for offensive fire attack.