Every opening in the walls, ceiling or roof needs a filter or screen at the facility boundary so that animals, invertebrates included, cannot get in or out. The filter or screen material has to be strong enough mechanically to bear any airflow load, survive routine cleaning undamaged, and hold up against both corrosion and animals, invertebrates included, getting through it.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.