What is the defining characteristic of a closed head steel drum?

A closed head steel drum is defined primarily by the lack of openings that lead to the interior of the drum, distinguishing it from other types of drums that may have removable lids or openings for access. The absence of openings is crucial for applications requiring the containment of materials, particularly hazardous substances, as it minimizes the risk of leaks, spills, or contamination. This characteristic makes closed head drums particularly useful for storing and transporting liquids, ensuring that the contents remain secure and protected from external environmental factors.

In contrast, options that suggest a removable lid or other closure methods imply the presence of openings, which does not align with the defining feature of closed head drums. Therefore, the lack of any openings is what fundamentally characterizes a closed head steel drum.