Which appliance uses the Venturi principle to introduce foam concentrate into a water stream?

The appliance that utilizes the Venturi principle to introduce foam concentrate into a water stream is the eductor. The Venturi principle describes how fluid flows through a constricted section of a pipe, resulting in a decrease in pressure and allowing surrounding liquid or gas to be drawn into the flow. In the context of firefighting, when water flows through the eductor at a sufficient velocity, it creates a low-pressure zone that pulls foam concentrate from a container into the water stream, mixing it before it is discharged.

This method is efficient for achieving the desired concentration of foam, making the eductor a widely used tool in various firefighting applications where foam is needed for combating flammable liquid fires. The focus on creating a vacuum allows for a continuous flow of foam concentrate without relying on pressurized foam systems, which can be advantageous in many scenarios.

In comparison, while the foam generator and metering device can also introduce foam concentrate, they do not operate based on the Venturi principle in the same way the eductor does. The foam nozzle is responsible for applying the foam to a fire, but it does not mix the concentrate with water; instead, it functions mainly to dispense the foam that is already mixed prior to reaching the nozzle. Thus, the ed