Which type of fire extinguisher does the picture symbol method not apply to?

The picture symbol method is primarily designed for use with fire extinguishers that handle common combustible materials, flammable liquids, and electrical fires. This method allows users to easily identify the appropriate type of extinguisher for various fire classes using universally recognized symbols.

Class D fire extinguishers, however, are specifically designed for use on fires involving combustible metals, such as magnesium, titanium, and sodium. These types of fires require specialized extinguishing agents and techniques that are not covered by the picture symbol method. Because the extinguishing processes for combustible metals are significantly different from those for Class A, B, and C fires, Class D extinguishers rely on different labeling and guidance materials tailored to handle these unique hazards effectively.

Consequently, the picture symbol method is not applicable to Class D extinguishers, which is why this option is the correct answer.