Positive-pressure ventilation is least suitable for which situation?

Positive-pressure ventilation (PPV) is designed to enhance fire suppression efforts by introducing fresh air into a space, which can help to push smoke, heat, and toxic gases out of the structure. However, it is least suitable for fires in structural void spaces.

When a fire is located in hidden or confined areas, such as within walls, ceilings, or other voids, applying positive-pressure ventilation can inadvertently spread the fire. This happens because forcing air into these spaces can create a pressure differential that drives smoke and heat further into the voids, potentially causing the fire to grow or be pushed into other areas of the structure. Additionally, the lack of direct access to these spaces makes it difficult to effectively control air flow using PPV.

In contrast, while PPV can be beneficial during a fire attack, in large interior spaces, or in high-rise fires, it is crucial to have an understanding of the fire's location and structure dynamics. In these contexts, PPV can help to improve visibility, provide safer operating conditions, and assist firefighting efforts when implemented correctly.