What is the term used for materials that are spontaneously combustible?

The term for materials that are spontaneously combustible refers to substances that can ignite without an external ignition source due to their chemical properties. This characteristic is recognized in the context of hazardous materials classification, particularly under the guidelines set forth in NFPA standards.

Hazard Class 148.1 specifically identifies materials that have a propensity to ignite spontaneously when exposed to air. This classification is crucial for responders to hazardous materials incidents, as it informs them of the potential risks associated with handling or being near these substances. Understanding and identifying spontaneously combustible materials helps ensure proper safety measures and response tactics during emergency situations.

In the context of the other choices, they relate to different classifications of hazardous materials that involve varying properties, such as toxicity or reactivity, but do not pertain to spontaneous combustion. This highlights the importance of understanding the specific characteristics outlined in the classification system to ensure the safety of responders and the public in hazardous material situations.