Class B fires involve flammable or combustible liquids such as gasoline, kerosene, and common organic solvents used in the laboratory. Class C fires involve energized electrical equipment, such as appliances, switches, panel boxes, power tools, hot plates and stirrers. Water is a particularly dangerous extinguishing medium for class C fires because of the risk of electrical shock. Class D fires involve combustible metals, such as magnesium, titanium, potassium and sodium as well as pyrophoric organometallic reagents such as alkyllithiums, Grignards and diethylzinc. Your fire extinguishers should have ABC ratings on them.
Higher numbers mean more firefighting power.
In this example, the extinguisher has a good firefighting capacity for Class A, B and C fires. Dry chemical extinguishers are useful for class ABC fires and are your best all around choice. They have an advantage over CO 2 extinguishers in that they leave a blanket of non-flammable material on the extinguished material which reduces the likelihood of reignition. Type BC fire extinguishers contain sodium or potassium bicarbonate. Type ABC fire extinguishers contain ammonium phosphate.