What type of foam does not require an aeration device?

The type of foam that does not require an aeration device is Class A foam. This foam is specifically designed for use on ordinary combustibles, such as wood and paper, and works by creating a thin film that helps to suppress the flames and cool the surface of the burning material. Class A foam can be mixed with water and is effective at reducing the surface tension of water, allowing it to penetrate into burning materials more effectively.

In contrast, Protein foam and Fluoroprotein foam are typically used for flammable liquids and do require aeration to generate the bubbles necessary for forming a stable foam blanket. AFFF (Aqueous Film Forming Foam) is designed to control flammable liquid fires and also relies on aeration to produce the effective film-forming action necessary to extinguish those types of fires. Because Class A foam does not need aeration to be effective, it stands out as the correct answer.