What is the expansion ratio for low-expansion foam?

Low-expansion foam is characterized by its specific expansion ratio, which typically ranges from 1:1 to about 20:1. This means that for every part of foam concentrate, it can produce up to 20 parts of finished foam. The purpose of this foam type is to provide effective coverage and smothering of flammable liquids, particularly in situations where it is important to minimize the foam's ability to expand rapidly.

When examining the expansion ratios, options indicating higher ratios (like 30:1 or 40:1) would pertain more to mediums or high-expansion foams, which are designed for specific applications and have different properties. Therefore, the assertion that the expansion ratio for low-expansion foam is less than 20:1 aligns with accepted standards and practical applications in firefighting. This ensures that firefighters can effectively manage flammable liquids by applying a foam solution that maintains sufficient density and stability on the surface of the fuel.