The class component of an explosion zone classification system determines the properties of hazardous materials present in any given environment. Hazardous materials are categorized into three main groups:

    Class I environments where hazards are flammable vapors and gases present in sufficient quantities to form explosive mixtures

    Class II hazardous materials are combustible dust present in quantities enough to trigger an explosion or ignite a fire

    Class III materials are fibers or flying particles present in an environment. These materials may or may not be sufficient to cause an explosion or start a fire