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

The correct answer identifies that oxygen is not classified as a type of fire extinguisher. Fire extinguishers are designed to suppress or extinguish fires by removing one or more elements of the fire triangle: heat, fuel, or oxygen.

Water-based, foam, and carbon dioxide extinguishers each serve specific purposes and are designed to combat different classes of fires. Water-based extinguishers are commonly used for Class A fires involving ordinary combustible materials, foam extinguishers can tackle both Class A and Class B fires (flammable liquids), and carbon dioxide extinguishers are effective for Class B and electrical fires, as they suffocate the flames by displacing oxygen.

Oxygen itself, however, is a critical component that fuels combustion rather than extinguishing fires. Therefore, it does not qualify as a fire extinguisher. This understanding highlights the essential principles of fire science and ensures the safe and effective use of fire suppression equipment.