What should never be used to extinguish a grease fire?

Water is not suitable for extinguishing a grease fire because it can cause the fire to escalate. When water is poured over a burning grease fire, it can lead to a phenomenon known as "boiling over." The water will sink beneath the oil, causing the heated oil to erupt and spread the flames even further. This reaction occurs because water is denser than oil, and the introduction of water can rapidly convert to steam, which expands and can carry burning grease with it, thus worsening the situation.

In contrast, options such as sand and baking soda are effective for smothering the fire, as they can eliminate the oxygen source and help to cool the flames. A fire extinguisher rated for grease fires can effectively put out the flames without exacerbating the situation. Knowing how to properly manage different types of fires is crucial for safety, particularly in kitchen settings where grease fires can occur.