CO2 extinguishers are the extinguisher of choice for electrical fires, but they also work on flammable liquid (class B) fires. You can find out more in our simple guide. CO2 fire extinguishers are primarily used for electrical fires and often paired with foam extinguishers. CO2 fire extinguisher uses: • Fires involving equipment such as computers, or generators (‘electrical’ fires) • Fires involving some flammable liquids, such as petrol, diesel, and paint (‘class B’ fires) Do not use CO2 extinguishers for: • Cooking fires involving oil and grease, such as chip pan fires (‘class F’ fires)