What supports the pleated fiberglass filter?

The pleated fiberglass filter is supported by a metallic mesh, which plays a crucial role in maintaining the structural integrity of the filter while allowing for adequate airflow. This mesh provides stability to the pleated design, preventing the filter media from collapsing or bending under pressure. The design of pleated filters allows for a larger surface area, which enhances their ability to capture particulates while the mesh provides necessary support and helps prevent damage during operation.

The other options do not accurately represent the supportive structure of pleated fiberglass filters. A diffuser layer, while beneficial in some filtration applications, does not serve as structural support in this context. Filter media itself is the component designed to capture contaminants but does not provide the necessary support to maintain the pleat configuration. The option of "None of the above" is incorrect as there is a specific component that does provide support, which is the metallic mesh.