What does the term "extension" refer to in firestop systems?

The term "extension" in firestop systems refers specifically to the expansion of firestop materials upon exposure to heat. When a fire occurs, the firestop products are designed to react to extreme temperatures by expanding to fill the openings and gaps in walls or floors, thus maintaining the integrity of the fire-rated assembly. This property is crucial because it enhances the effectiveness of the firestop system in preventing the spread of fire and smoke through penetrations, ensuring that the safety measures in place are functional during a fire incident.

Understanding this concept is vital, as the expansion capability of firestop materials directly impacts their performance during a fire emergency. Firestop products that do not expand or are not designed to respond to heat may fail to provide the necessary barrier, thereby compromising safety. The other options do not encapsulate this fundamental aspect of firestop systems, focusing instead on physical dimensions, material movement, or joint width, which do not pertain specifically to the critical characteristic of heat-induced expansion.