Which statement about the six-inch rule for Class B fire suppression sweeps is correct?

Which statement about the six-inch rule for Class B fire suppression sweeps is correct?

• A. Each sweep must extend at least 6 inches past the edges of the fire
• B. Each sweep must be within 6 inches of the fire's center
• C. Sweeps should be made only vertically
• D. Sweeps should not pass beyond the flames

Answer: (A)

Understanding how a Class B fire suppression sweep works helps you see why extending beyond the fire’s edge is essential. For flammable-liquid fires, the goal is to cool and cover the entire burning area, including its perimeter, so the fuel at the edge doesn’t continue to burn or flash back. Extending each sweep at least 6 inches past the edges creates a buffer zone that ensures the outer boundary is fully treated, reducing the chance of reignition and helping prevent the fire from spreading outward. Sweeping only near the center would leave the outer edge uncooled and vulnerable. Sweeping only vertically misses the broad surface of a liquid pool and won’t effectively cover the horizontal spread. Not passing beyond the flames would leave the outer edge untreated, allowing continued burning along the boundary.

Understanding how a Class B fire suppression sweep works helps you see why extending beyond the fire’s edge is essential. For flammable-liquid fires, the goal is to cool and cover the entire burning area, including its perimeter, so the fuel at the edge doesn’t continue to burn or flash back. Extending each sweep at least 6 inches past the edges creates a buffer zone that ensures the outer boundary is fully treated, reducing the chance of reignition and helping prevent the fire from spreading outward.

Sweeping only near the center would leave the outer edge uncooled and vulnerable. Sweeping only vertically misses the broad surface of a liquid pool and won’t effectively cover the horizontal spread. Not passing beyond the flames would leave the outer edge untreated, allowing continued burning along the boundary.