What are the main characteristics of Class A foam?

Class A foam is specifically designed for use with ordinary combustibles such as wood, paper, and some plastics. Its main characteristics include low viscosity, which allows it to effectively penetrate and cool combustible materials, enhancing its ability to extinguish fires. This foam works by forming a film on the surface of the burning material, which helps to smother the fire and prevent re-ignition.

The effectiveness of Class A foam on ordinary materials is crucial because it addresses common fire scenarios encountered in residential and commercial structures. By creating a barrier with the foam, it encapsulates the fuels and minimizes the release of flammable vapors.

While other choices may contain elements related to foam characteristics, they do not describe the primary attributes and intended usage of Class A foam as accurately as its effectiveness on ordinary combustibles combined with its low viscosity.