Aircraft releases fire retardant. An airtanker releases fire retardant over land projected to be in the path of a forest fire. A firefighter (lower centre) carries a pulaski axe which is used to dig areas of the ground and clear it free from combustible material. This area is known as a firebreak. Fire retardants are normally composed of ammonium sulphate or ammonium polyphosphate with various additives such as thickeners, wetting agents and preservatives. They are often coloured red to indicate areas where the retardant has fallen. Photographed in 2000 at Rangely, Colorado, USA.