Which agent is most effective to use on a lithium battery that has burned or ruptured?

Using a Class D extinguisher on a lithium battery fire is the most effective course of action due to the unique combustibility and reactivity of lithium. Lithium burns at high temperatures and can react violently with water and other common fire suppression agents, potentially worsening the situation.

Class D extinguishers are specifically designed for fires involving combustible metals, including lithium. They contain agents that smother the fire by forming a protective layer over the burning material, effectively separating the fuel from oxygen, which is essential in extinguishing metal fires. This is crucial in preventing reignition and ensuring safe containment of the fire.

In contrast, using CO2, Halon, or water can lead to ineffective fire suppression or exacerbate the fire, especially with water, which can react with lithium to produce flammable hydrogen gas. This makes understanding the appropriate fire extinguishing agents for different types of fires essential for effective fire safety and incident management.