Ball Valve — Valve having a ball-shaped internal component with a hole through its center that permits water to flow through when aligned with the waterway.
Broken Stream — Stream of water that has been broken into coarsely divided drops.
Class A Foam — Foam specially designed for use on Class A combustibles. These foams are becoming increasingly popular for use in wildland and structural fire fighting. Class A foams, hydrocarbon-based surfactants, are essentially wetting agents that reduce the surface tension of water and allow it to soak into combustible materials easier than plain water.
Class B Foam — Foam fire-suppression agent designed for use on un-ignited or ignited Class B flammable or combustible liquids.
Cooling —Reduction of heat by the quenching action or heat absorption of the extinguishing agent.
Eduction — Process used to mix foam concentrate with water in a nozzle or proportioner; concentrate is drawn into the water stream by the Venturi method; also called induction.
Film Forming Fluoroprotein Foam (FFFP) — Foam concentrate that combines the qualities of fluoroprotein foam with those of aqueous film forming foam.
Fire Stream — Stream of water or other water-based extinguishing agent after it leaves the fire hose and nozzle until it reaches the desired point.
Foam — Extinguishing agent formed by mixing a foam concentrate with water and aerating the solution for expansion; for use on Class A and Class B fires. Foam may be protein, synthetic, aqueous film forming, high expansion, or alcohol type. Also known as Finished Foam.
Fog Nozzle — Nozzle that can provide either a fixed or variable spray pattern. The nozzle breaks the foam solution into small droplets that mix with air to form finished foam.
Fog Stream — Water stream of finely divided particles used for fire control.
Handline Nozzle — Any nozzle that can be safely handled by one to three firefighters and flows less than 350 gpm (1 400 L/min).
Injection — Method of proportioning foam that uses an external pump or head pressure to force foam concentrate into the fire stream at the correct ratio for the flow desired.
In-Line Eductor — Eductor that is placed along the length of a hoseline.
Latent Heat of Vaporization — Quantity of heat absorbed by a substance at the point at which it changes from a liquid to a vapor.
Material Safety Data Sheet (MSDS) — Form provided by the manufacturer and blender of chemicals that contains information about chemical composition, physical and chemical properties, health and safety hazards, emergency response procedures, and waste disposal procedures of the specified material.
Nozzle Pressure — Velocity pressure at which water is discharged from the nozzle.
Polar Solvents — Flammable liquids that have an attraction for water, much like a positive magnetic pole attracts a negative pole; examples include alcohols, ketones, and lacquers.
Premixing — Mixing premeasured portions of water and foam concentrate in a container. Typically, the premix method is used with portable extinguishers, wheeled extinguishers, skid-mounted twin-agent units, and vehicle-mounted tank systems.
Proportioning —Mixing of water with an appropriate amount of foam concentrate to form a foam solution.
Separating — Act of creating a barrier between the fuel and the fire.
Smothering — Act of excluding oxygen from a fuel.
Solid Stream — Hose stream that stays together as a solid mass as opposed to a fog or spray stream. A solid stream is produced by a solid-bore nozzle and should not be confused with a straight stream.
Vaporization — Process of evolution that changes a liquid into a gaseous state. The rate of vaporization depends on the substance involved, heat, and pressure.
Venturi Principle — Physical law stating that when a fluid, such as water or air, is forced under pressure through a restricted orifice, there is an increase in the velocity of the fluid passing through the orifice and a corresponding decrease in the pressure exerted against the sides of the constriction. Because the surrounding fluid is under greater pressure (atmospheric), it is forced into the area of lower pressure. Also called Venturi Effect.
Water Hammer — Force created by the rapid deceleration of water causing a violent increase in pressure that can be powerful enough to rupture piping or damage fixtures. It generally results from closing a valve or nozzle too quickly.