Red phosphorus combustion. The flames die down when covered and reignite when uncovered. Red phosphorus burns in air, forming white fumes of phosphorus pentoxide. Phosphorus is a reactive element that is only ever found in compounds in nature, but exists as several distinct allotropes as an element. Red phosphorus is formed by heating the extremely reactive white phosphorus in the absence of oxygen or by exposing white phosphorus to sunlight. Red phosphorus burns at around 300 degrees Celsius.