What is a common material type that is stored in drums?

Drums are commonly used for the storage of a variety of materials, and food-grade materials are one of the significant types associated with drum storage. Food-grade materials are substances that meet safety requirements for food contact, ensuring they do not pose a risk to human health or contaminate food products. When stored in appropriate drums, these materials remain protected from contamination, spills, and environmental factors, which is crucial in maintaining food safety.

In contrast to food-grade materials, the other options do not represent a comprehensive scope of substances that can be stored in drums. While liquids are commonly stored in drums, they are not the only type of material; thus, stating 'only liquids' is too restrictive. Compost, while it can be stored in various containers, is typically not associated with drum storage in the context of hazardous materials. Lastly, the emphasis on 'only flammable materials' excludes a wide range of other materials, including non-flammable substances, that can be safely stored in drums. The versatility of drums as a storage option highlights the importance of classifying materials appropriately, particularly those that are food-grade.