In the case of a class A solid fire, which of the following extinguishers would be least effective?

In the context of a Class A fire, which involves ordinary combustible materials like wood, paper, and textiles, the effectiveness of different types of fire extinguishers varies significantly.

Water is a highly effective extinguishing agent for Class A fires because it cools the burning material and can help prevent re-ignition. Foam extinguishers can also work on Class A fires by forming a barrier between the fuel and the air, although their primary use is for flammable liquids. Wet chemical extinguishers are typically used for cooking oils and fats, which are classified as Class K fires. However, these extinguishers can also suppress Class A fires to some extent by cooling and creating a layer that prevents oxygen from reaching the fuel.

In contrast, carbon dioxide (CO2) extinguishers are less effective against Class A fires. While CO2 is excellent for flammable liquids and electrical fires because it displaces oxygen, it does not cool the material sufficiently and may not effectively extinguish a fire involving solid combustibles. Without cooling, the materials can quickly reignite once the CO2 dissipates. Thus, despite being a powerful extinguishing agent for certain fire classes, CO2 does not provide the necessary cooling effect that is crucial for combating Class