What surrounds a chimney passing through a floor or ceiling?

The area surrounding a chimney that passes through a floor or ceiling is known as a firestop. This component is critical in maintaining the safety and integrity of a building. The firestop serves to prevent the spread of fire and smoke from one area of a structure to another, effectively sealing gaps around the chimney in both horizontal and vertical assemblies. It acts as a barrier, ensuring that any potential fire that originates from the chimney does not have an easy route to propagate through the building's floors and ceilings.

Other components like support and insulation play important roles as well, with support providing structural integrity to the chimney and insulation potentially reducing heat transfer. However, they do not specifically address the fire safety aspect that the firestop is designed for. A firewall is a different concept, primarily functioning as a barrier to protect adjacent spaces from the spread of fire and is typically found as a dedicated wall section rather than around a chimney penetration. The firestop is essential in meeting building codes and ensuring that the installation complies with safety regulations, making it the correct choice in this context.