Foam Expansion is defined as:

• A. The finished foam after aeration.
• B. Result of adding air to a foam solution; expansion creates the foam bubbles that result in finished foam or foam blanket.
• C. A device that injects concentrate into water.
• D. The foam concentrate.

Answer: (B)

Foam expansion describes how much foam volume is produced when air is introduced into a foam solution. As air is added, bubbles form and the liquid expands into a larger foam blanket. This expansion, or expansion ratio, is what links the original concentrate to the amount of foam you get. The finished foam or foam blanket is the product that results from this expansion, not the act of expanding itself. The other options refer to either the final foam state, a device, or the concentrate itself, which are different concepts.