Which type of fire extinguisher is designated for use with plain water?

The type of fire extinguisher designed for use with plain water is classified as Class A. This designation indicates that these extinguishers are intended for fires involving ordinary combustibles such as wood, paper, cloth, and some types of plastics. Water is effective in such cases because it can cool the burning material below its ignition temperature and can also help to smother the fire by displacing oxygen.

Fire extinguishers classified as Class B are meant for flammable liquids and can contain materials such as gasoline, oil, and grease, which cannot be extinguished with water. Class C extinguishers are used for electrical fires and would not be suitable for water since it conducts electricity and poses a risk of shock. Class D extinguishers are specifically for combustible metals, such as magnesium and sodium, which also require specialized extinguishing agents other than water. Using water in these scenarios could be dangerous or ineffective.

Therefore, Class A extinguishers are the only type explicitly designed for use with plain water, making it critical to use them appropriately for fighting fires involving solid combustibles.