What are the two greatest threats to multiple dwelling structures in the event of a fire?

In the context of fires in multiple dwelling structures, pipe chases and channel rails represent significant threats due to their role in fire spread and the facilitation of smoke movement throughout the building. Pipe chases, which are vertical spaces that allow service pipes to be run between floors, can act as conduits for flames and smoke, enabling fire to travel rapidly between levels of a structure. This can compromise the safety of residents and the effectiveness of firefighting operations.

Channel rails, which are often found in multi-story buildings, can also contribute to the rapid spread of fire. They can trap heat and allow fire to extend horizontally, affecting multiple units quickly. This makes both pipe chases and channel rails critical considerations for fire officers when assessing the situation and formulating a firefighting strategy.

Other options, while they may present risks or concerns during a fire incident, do not pose the same level of immediate threat to life safety and structural integrity as the conduits provided by pipe chases and channel rails. Fire alarms and sprinkler systems, for example, are actually designed to enhance safety and mitigate fire spread. Walls and ceilings can contain fires, but they also have limitations in preventing fire from spreading if breached. Electric wiring and furniture, while they can introduce hazards, are