What class of extinguishing agents interrupts the chain reaction of fire chemicals?

The classification of extinguishing agents that interrupts the chain reaction of fire is represented by Class K. These agents are specifically designed for use on fires involving cooking oils and fats, which are common in kitchens. Class K fire extinguishers utilize agents such as potassium acetate, which not only cools the fire but also forms a barrier that prevents re-ignition by interrupting the chemical chain reaction. This makes them particularly effective in extinguishing these types of fires, as they address both the fuel and the chemical reactions occurring.

Class B extinguishing agents are typically used for flammable liquids, while Class A agents are suitable for ordinary combustibles like wood and paper, and Class D agents are specifically designed for metal fires. Each class operates based on different principles and targets different fire types, but it is Class K that directly interrupts the fire's chemical reactions, making it the correct choice in this context.