Wisconsin Firefighter 1 Practice Test 2026 - Free Firefighter Exam Practice Questions and Study Guide

A CO2 extinguisher is effective in Class B and C fires because it works by displacing oxygen, which is essential for combustion. Fires classified as Class B involve flammable liquids such as gasoline and oil, while Class C fires involve energized electrical equipment. When CO2 is released from the extinguisher, it creates a blanket of carbon dioxide that suffocates the fire by reducing the oxygen levels around it, thus inhibiting the fire's ability to continue burning.

Both Class B and C fires require specific extinguishing agents for effective suppression, and CO2 is particularly useful in electric fires since it does not conduct electricity, making it safe for use on live electrical equipment. Other types of extinguishers, like water-based and foam, can be ineffective or even dangerous when used on Class C fires, as water can conduct electricity and potentially worsen the situation.