What is the primary function of a fire wall in a building?

The primary function of a fire wall in a building is to limit flame spread. Fire walls are strategically designed barriers that help to contain a fire within a specific area or compartment of a building. By preventing the movement of flames and heat from one section to another, fire walls serve as crucial safety features that protect occupants and property by allowing more time for evacuation and fire-fighting efforts. They are typically constructed with non-combustible materials and extend from the foundation through the roof, creating a robust barrier against fire penetration.

In addition to limiting flame spread, fire walls also provide structural support and can be used to divide interior spaces, but these functions are secondary to their primary role in fire safety. Controlling moisture is not a function related to fire walls, as this is typically managed through other building components like waterproofing materials. Therefore, option B aligns directly with the critical safety objectives of fire prevention and protection within a building's design.