ELI5: Explain Like I'm 5

Packing (firestopping)

Packing (firestopping) is the process of using special material to fill in gaps between building walls and floors to stop fire and smoke from spreading. It's like stuffing a pillow into a big hole, but with special materials that are designed to be resistant to extreme heat, smoke, and fire. These materials form a barrier that helps to prevent fire from spreading from one part of the building to another.