Any opening in the walls, ceiling or roof has to be screened or filtered where it meets the boundary so animals, invertebrates included, cannot enter or leave. The filter or screen material must be strong enough to bear any airflow load, survive regular cleaning undamaged, and resist corroding and being penetrated by animals and invertebrates.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.