What is indicated by a star with the letter D on a fire extinguisher?

A star with the letter D on a fire extinguisher indicates that it is specifically designed for use on combustible metals, such as magnesium, sodium, or potassium. This class of extinguishers is important because metal fires cannot be extinguished with water or traditional extinguishing agents; they require special agents that can smother the fire or remove the heat.

The association of the letter D with general combustible materials is misleading. While general combustible materials may be addressed by other fire extinguisher classes, a D-rated extinguisher is quite unique in its application. Therefore, while it might seem intuitive to link a D designation to brake fires or flammable liquids, those situations typically require different classes of extinguishers.

In summary, the correct identification of the letter D emphasizes the specialized nature of the extinguisher, which operates effectively on dangerous metal fires, ensuring safety in environments where these materials are present.