Penetrant (mechanical, electrical, or structural)

Penetrants, or penetrating items, are the mechanical, electrical or structural items that pass through an opening in a wall or floor, such as pipes, electrical conduits, ducting, electrical cables and cable trays, or structural steel beams and columns. When these items pierce a wall or floor assembly, they create a space between the penetrant and the surrounding structure which can become an avenue for the spread of fire between rooms or floors.

Source: Wikipedia — Penetrant (mechanical, electrical, or structural) (CC BY-SA 4.0)