Combustion of a sample of elemental phosphorus as it is heated in air. Phosphorus is a non-metallic element that exists in several forms, or allotropes. This is red phosphorus, which is highly reactive and combustible, and burns in atmospheric oxygen with an orange flame. Burning red phosphorus in air produces toxic phosphorus pentoxide gas. This clip has been sped up in the middle section, and also has the light removed to show details of the flame and residue.