What must be securely fastened in place in all spaces between chimneys and through which they pass?

The requirement for securely fastening noncombustible material in all spaces between chimneys and through which they pass is crucial for safety and compliance with building codes. Noncombustible materials are essential because they help to prevent the transfer of heat from the chimney to combustible materials in the surrounding area. This is particularly important to minimize the risk of fire hazards.

Properly installed noncombustible materials create a barrier that controls and mitigates the high temperatures that may radiate from the chimney. They ensure that any potential ignition sources are kept away from flammable materials, thus enhancing the overall fire safety of the building. This practice also helps to meet industry standards and building regulations, which are designed to protect structures and occupants from fire risks associated with chimney installations.

In contrast, leaving openings filled with combustible materials or insufficient barrier systems can lead to dangerous situations, making it imperative to follow regulations that call for the use of noncombustible materials in these scenarios.