Carbon dioxide (CO2) can exist in three states: solid (dry ice), liquid, and gas. In the context of a fire extinguisher, carbon dioxide is stored under high pressure in its gaseous state. When you operate a CO2 fire extinguisher, the pressure is released, allowing the gas to escape rapidly.
While carbon dioxide can be liquefied under specific conditions of temperature and pressure, it is not typically stored as a liquid in fire extinguishers. The pressure inside the extinguisher keeps the CO2 in its gaseous state.
When you activate a CO2 fire extinguisher, you typically press a handle or lever, which opens a valve. This valve allows the pressurized carbon dioxide gas to flow from the extinguisher into the atmosphere. The sudden release of gas creates a high-velocity jet that helps suppress the fire.
The movement of carbon dioxide during the discharge process primarily occurs in the form of a rapidly expanding gas jet. The force of the gas being expelled from the extinguisher helps to displace oxygen from the fire area, reducing the oxygen concentration and suppressing the flames. Carbon dioxide is effective at extinguishing fires because it can displace oxygen and also cool the fire by absorbing heat.
It's important to note that the liquid state of carbon dioxide is not involved in the operation of a typical fire extinguisher. CO2 fire extinguishers are designed to utilize the gas phase of carbon dioxide for firefighting purposes.