Which of the following is NOT a type of fire extinguisher?

Sodium bicarbonate is not classified as a standalone type of fire extinguisher, which makes this the correct answer. While sodium bicarbonate can be an ingredient in certain types of firefighting agents, it is primarily known for its use in fire suppression when it acts as a dry chemical that can help extinguish small grease fires, particularly in cooking environments, rather than being classified as a type of extinguisher itself.

On the other hand, DCP (Dry Chemical Powder), ABC (a classification that denotes an extinguisher capable of fighting Class A, B, and C fires), and foam extinguishers are recognized categories of fire extinguishers with specific applications and classifications. DCP extinguishers are widely used for various types of fires due to their versatility, while foam extinguishers are effective for flammable liquid fires. Understanding these classifications is crucial for identifying the appropriate extinguisher for different fire situations.