Associate Safety Professional Practice Exam

What type of combustible material is categorized under Class D?

1. Cooking oil

2. Grease

3. Sodium and lithium

4. Paint

The correct answer is: Sodium and lithium

Class D combustible materials are specifically categorized as reactive metals, which include substances like sodium and lithium. These materials are distinguished by their ability to spontaneously ignite or react violently when they come into contact with water or moisture, and they require special handling and extinguishing methods, such as dry powder extinguishers specifically designed for metal fires. In contrast, cooking oil and grease, while they can be flammable and are serious fire hazards, do not fit into Class D. They are typically categorized under Class K (for cooking oils and fats) or Class B (flammable liquids). Paint can also be flammable but is classified under Class B materials due to its liquid form and combustibility. Therefore, the classification of sodium and lithium as Class D substances is correct due to their unique properties and the specific fire suppression techniques needed to address fires involving these reactive metals.