Which hazard describes a substance that can spontaneously combust in the presence of oxygen?

Pyrophoric materials are those that can ignite spontaneously in the presence of air or oxygen at temperatures of 130 °F (54 °C) or below. This characteristic makes them particularly hazardous in environments where they may come into contact with oxygen, as they can pose a significant fire risk without any external ignition source. Understanding this property is crucial for safe handling and storage, especially in industries that work with such materials.

In contrast, flammable substances require an external ignition source to combust, while explosives have a different hazard profile, involving a rapid release of energy and pressure when undergoing a reaction. Organic peroxides are a category of chemicals that can be hazardous as they can decompose, potentially leading to explosions; however, they do not specifically describe the ability to ignite spontaneously like pyrophoric materials do.