Which device mixes foam concentrate in the water stream in the proper percentage?

The device that effectively mixes foam concentrate with water in the correct proportions is known as a proportioner. This equipment is crucial in firefighting as it ensures that the foam is created at the right ratio to effectively suppress fires, especially those involving flammable liquids.

Proportioners work by drawing the foam concentrate from a storage tank and mixing it with water in a precise amount based on the fire suppression needs. This controlled blending is essential for achieving the desired characteristics of the foam, which include its ability to form a barrier against flames and cool the burning surface. Proper foam formulation can make a significant difference in firefighting effectiveness, particularly in protecting areas where flammable liquids are present.

Other devices, such as mixers, aerators, and aspirators, serve different functions in fluid dynamics or foam creation but do not specifically ensure the correct proportional mixing of foam concentrate and water, which is the primary functionality of a proportioner.