Which class in DOT regulations is categorized by the risks posed by spontaneous combustion?

The classification that addresses the risks associated with spontaneous combustion falls under Class 4 in the Department of Transportation (DOT) regulations. Specifically, Class 4 materials are divided into two key categories: flammable solids and substances that can easily ignite without external ignition sources, which includes materials that can spontaneously combust. This classification is critical for ensuring safe handling, transportation, and storage, as spontaneous combustion poses significant risks both during transport and while in storage, potentially leading to dangerous fire incidents.

Class 2 primarily deals with gases, and Class 3 is for flammable liquids. Class 9 encompasses miscellaneous dangerous substances that do not fit into the other classes but do pose various risks. Understanding these distinctions helps in effectively managing hazardous materials and protecting responders, facilities, and the public.