Simply put, a fire extinguisher is an active protection device. They come in two common categories – a hand-held cylindrical fire extinguisher used to extinguish small fires in homes, schools, offices, etc., or larger containers as wheeled fire extinguishers used to combat larger fires such as those occurring in industrial and commercial settings.
Fire extinguishers are pressurized to produce a powerful spray upon discharge. They come in stored pressure or cartridge-operated types. In stored pressure extinguishers the propellent is stored in the same chamber as the active fire fighting agent. When the agent is a dry chemical, nitrogen is typically used as the propellent. When the agent is water or a foam, air is the typical propellent used.
Cartridge-operated extinguishers house the propellent gas in a separate cartridge. When activated the cartridge is punctured, mixing the contents, expelling both under pressure. Carbon Dioxide is typically used in these types of units. These types of fire extinguishers are used primarily in industrial facilities. They have the advantage of simple and prompt recharge for quick return to the fire.
An understanding of the different classifications (Classes) of fires is helpful in determining which type of fire extinguisher is best for your situation. Below is a helpful chart explaining the different Classes of Fires and their unique characteristics such as their typical fuel source, the setting in which a type of fire typically occurs, and the most effective type of fire extinguisher to use in combating the fire. The second chart below provides a breakdown of the various types of fire extinguishers, the fire fighting agents used, their advantages/uses and disadvantages.