Final answer:
Fire extinguisher labels with multiple letters can handle multiple types of fires, with each letter indicating a specific class of fire it is suitable for.
Step-by-step explanation:
When a fire extinguisher's label displays multiple letters, it indicates that the extinguisher is designed to handle multiple types of fires. Each letter corresponds to a class of fire that the extinguisher is equipped to put out. 'A' is for ordinary combustibles like wood and paper, 'B' is for flammable liquids such as gasoline and oil, 'C' indicates suitability for electrical fires, and 'D' is for fires involving combustible metals, like magnesium or titanium. Special extinguishing agents, like fluorinated foams or dry powders, address specific types of fires, like those from organic liquids or metals, respectively. The National Fire Protection Agency (NFPA) 704 Hazard Identification System provides additional safety information about flammable and hazardous substances, which is important to understand when selecting and using fire extinguishers.