Which of the following indicates that nozzle pressure should be increased?

• A. Decreased engine RPM
• B. Observed insufficient extinguishing effect or continuing flame growth despite current pressure.
• C. Water flow is constant
• D. Nozzle is spraying a fine mist

Answer: (B)

When you’re deciding whether to raise nozzle pressure, watch how the fire responds to the water you’re delivering. If you’re not getting enough extinguishing effect and flames keep growing even though you’re already applying water, that’s a sign the current pressure isn’t enough to penetrate and cool the fuel and heat enough to stop the fire. Increasing nozzle pressure boosts the water’s velocity and reach, improves penetration into the flames, and enhances cooling by producing more steam and a stronger, more effective knockdown. This helps push back the heat and deny the fire the energy it needs to continue burning.

The other scenarios don’t directly indicate the need to increase nozzle pressure. A drop in engine RPM typically lowers pump discharge pressure, which could reduce the effectiveness rather than signal the correct response. A constant water flow doesn’t tell you how well that flow is doing its job at the nozzle—you assess performance rather than flow rate alone. A nozzle spraying a fine mist can mean a fog pattern or low pressure, but it isn’t in itself a reliable indicator that you should increase pressure; it could be a chosen fog setting or another condition.