Which best defines a master stream?

• A. A deck gun or monitor flowing more than 350 GPM
• B. A small handline under 50 GPM
• C. A foam nozzle used for ventilation
• D. A portable water extinguisher

Answer: (A)

A master stream is a high-volume water stream produced by a fixed or remotely controlled device, such as a deck gun or monitor, capable of delivering about 350 gallons per minute (GPM) or more. This large flow gives you the ability to reach distant parts of a fire and apply a heavy slosh of water to quickly knock down flames and cool exposed surfaces. The deck gun or monitor is specifically designed to provide that big, columnar stream from a fixed location or controlled remotely, which is the defining feature of a master stream.

The other options describe much smaller flows or different uses: a small handline under 50 GPM is a typical attack line, not a master stream; a foam nozzle used for ventilation isn’t about a high-volume stream and isn’t a master stream device; a portable water extinguisher is a small, handheld unit not capable of the large flows associated with master streams.