What is the primary risk associated with using water as an extinguishing agent on grease fires?

Using water as an extinguishing agent on grease fires carries the primary risk of spreading the fire. When water is applied to burning grease, it can cause the hot grease to splatter and spread flames to surrounding areas. This occurs because water is denser than oil, and when it comes into contact with the hot grease, it can rapidly evaporate, creating steam. The violent reaction can propel burning grease into the air, igniting additional flammable surfaces and spreading the fire beyond its original confines.

Effectively addressing grease fires requires methods that involve smothering the flames or using agents specifically designed to extinguish such fires, like Class K fire extinguishers, which are designed to combat cooking oil fires without causing flare-ups. Understanding these principles is crucial for managing the risks associated with different types of fires in a firefighting context.