How is the expansion of foam determined in a proportioning system?

• A. Expansion is determined by a ratio of the solution volume to the completely expanded foam volume.
• B. Expansion depends on foam color.
• C. Expansion is fixed and not adjustable.
• D. Expansion is determined by system pressure.

Answer: (A)

In a proportioning foam system, how much foam you get is tied directly to how much concentrate you feed and how much foam that concentrate becomes when fully expanded. The expansion is expressed by the ratio of the solution volume you introduce to the volume of foam produced after expansion. In other words, for every unit of concentrate that goes into the system, you end up with a larger volume of foam, and that relationship—concentrate volume to expanded foam volume—defines the expansion.

For example, if 1 gallon of concentrate yields 25 gallons of foam, the expansion is 25:1. This expansion is set by the system’s metering and nozzle design, not by foam color, and while system pressure can influence flow characteristics, it doesn’t establish the basic expansion ratio.