What does it mean when a fire extinguisher has a pictograph with a red slash through it?

A fire extinguisher displaying a pictograph with a red slash through it indicates that it is unsafe to use that particular extinguisher on the class of fire represented by the pictograph. This visual cue serves as a crucial safety measure, guiding fire responders to avoid ineffective or potentially dangerous actions during a fire emergency.

For instance, if an extinguisher designed for Class A fires shows a pictograph with a red slash indicating Class B fires, it warns users that using that extinguisher on flammable liquids (Class B) could lead to failure in suppressing the fire and risk exacerbating the situation. Understanding these symbols is vital for effective firefighting and ensuring safety for both responders and civilians.