For ease of identification, labels A, B, C, D, and K (and, more recently, pictograms) indicate the type of fire on which one can use an extinguisher.

Type Materials Description Label Pictogram
A Ordinary Combustibles Fires in paper, cloth, wood, rubber, and many plastics require a water or dry chemical type extinguisher labeled A. A: Combustibles Pictogram A
B Flammable Liquids Fires in solvents and other flammable liquids require dry chemical, Halon™, or CO² extinguisher labeled B. B: Liquids Pictogram B
C Electrical Equipment Fires in wiring, fuse boxes, energized equipment and other electrical sources require a dry chemical, Halon™, or CO² extinguisher labeled C. C: Electrical Equipment Pictogram C
D Metals Combustible metals such as magnesium and sodium require special extinguishers labeled D. D: Combustible Metals Pictogram D
K Cooking Oils and Fats Wet chemical extinguishers specially designed to put out fires of cooking oils or fats are labeled K; unlikely to be needed in a laboratory setting. K: Combustible Cooking Pictogram K

Most chemical laboratory fire hazards require multipurpose dry chemical extinguishers (ABC) located in hallways. “Gas” extinguishers containing carbon dioxide (CO2) offer a first defense against flammable liquids or electrical fires without leaving a powder residue that could harm electronic equipment. Halon™ 1211 fire extinguishers are no longer to be used on campus. If your lab has one, contact EHS so that it can be replaced.