Which type of fire extinguisher should not be used on a grease fire?

Using a water extinguisher on a grease fire can lead to dangerous situations. Grease fires, often found in kitchens from cooking oils, can reach extremely high temperatures. When water is applied to a grease fire, it does not effectively extinguish the flames. Instead, water can cause the burning grease to splatter explosively, spreading the fire and increasing the risk of even larger flames.

In contrast, other types of extinguishers, such as CO2, dry chemical, and foam extiguishers, are designed to be effective on grease fires. CO2 extinguishers displace oxygen, effectively smothering the fire, while dry chemical extinguishers create a barrier between the fuel and the fire, suppressing flames efficiently. Foam extinguishers can also work by forming a blanket over the burning grease, preventing oxygen from fueling the fire. Therefore, using water is dangerous and can worsen the situation, which is why it is the incorrect choice for handling a grease fire.