One of the most important duties of a fire warden is to understand the different types of fires that can occur, as each type requires a different approach to extinguish it. Class A fires involve solid materials such as wood, paper, rubber, plastic and cloth, and can be extinguished by using water-based fire extinguishers. Class B fires involve flammable or combustible liquids, such as petrol, oil and paint, and can be extinguished by using foam- or CO2-based fire extinguishers. Class C fires involve flammable gases, such as propane, butane and methane, and can be extinguished by using dry powder fire extinguishers. Class D fires involve flammable metals, such as potassium, aluminium and titanium, and can be extinguished by using dry powder fire extinguishers. Class F fires involve cooking oils and fats, and can be extinguished by using water-based fire extinguishers. With this knowledge in hand, fire wardens can ensure that everyone in their building is safe in the event of a fire.