Which statement correctly describes nozzle pressure requirements for fog and smooth bore nozzles?

• A. Fog nozzles require no nozzle pressure
• B. Smooth bore requires higher nozzle pressure than fog
• C. Fog nozzles may require higher nozzle pressure than smooth bore
• D. Nozzle pressure is not affected by nozzle type

Answer: (C)

Nozzle pressure is the pressure at the nozzle exit required to deliver the desired flow and pattern, and it depends on how the nozzle is built to shape the water. Fog nozzles atomize water to a broad spray, which involves internal pathways and sometimes air mixing that create energy losses inside the nozzle. To push the same amount of water through those internal passages and still achieve the Fog pattern, you typically need more pressure at the nozzle. If pressure is too low, the water won’t atomize properly and the pattern can collapse or become inconsistent.

Smooth bore nozzles, by contrast, produce a solid stream or a simple, wide fan with fewer internal losses. They can deliver the same flow at a lower nozzle exit pressure, so the required pressure is generally less than that for a fog nozzle.

Therefore, it’s accurate to say fog nozzles may require higher nozzle pressure than smooth bore to achieve the intended flow and spray characteristics. The other statements run counter to how nozzle design affects pressure requirements, since nozzle pressure does depend on the type and not all nozzles operate at zero pressure.