Which class is appropriate for extinguishing ordinary combustibles using a stored-pressure water extinguisher?

Which class is appropriate for extinguishing ordinary combustibles using a stored-pressure water extinguisher?

• A. CO2
• B. Stored-pressure water
• C. Dry chemical
• D. Foam

Answer: (B)

Water is the most effective for fires involving ordinary combustibles (Class A) because it absorbs a lot of heat. A stored-pressure water extinguisher delivers a powerful stream that cools the fuel (wood, paper, textiles) so its temperature drops below ignition, stopping the combustion process. Other agents don’t provide the same cooling effect: CO2 displaces air but doesn’t cool the fuel, so embers can reignite; dry chemical can interrupt chemical reactions but doesn’t remove heat as efficiently and can leave a messy residue; foam blankets the surface but still relies on water and is often more suited to liquid fires or mixed fuel scenarios. For straightforward Class A fires, a stored-pressure water extinguisher is the best choice because cooling the fuel is the most reliable way to stop the fire.

Water is the most effective for fires involving ordinary combustibles (Class A) because it absorbs a lot of heat. A stored-pressure water extinguisher delivers a powerful stream that cools the fuel (wood, paper, textiles) so its temperature drops below ignition, stopping the combustion process. Other agents don’t provide the same cooling effect: CO2 displaces air but doesn’t cool the fuel, so embers can reignite; dry chemical can interrupt chemical reactions but doesn’t remove heat as efficiently and can leave a messy residue; foam blankets the surface but still relies on water and is often more suited to liquid fires or mixed fuel scenarios. For straightforward Class A fires, a stored-pressure water extinguisher is the best choice because cooling the fuel is the most reliable way to stop the fire.