All portable fire extinguishers use what means for expelling their contents?

All portable fire extinguishers utilize pressure to expel their contents. Fire extinguishers are designed with a pressurized canister that holds the extinguishing agent, which can be water, foam, powder, CO2, or other chemicals specific to the type of fire being fought. When the operator squeezes the handle or pulls the pin, this pressure is released, allowing the extinguishing agent to flow out through the nozzle or nozzle attachment aimed at the fire.

The reliance on pressure is crucial for the effective operation of these extinguishers, as it ensures that the extinguishing agent can reach the fire quickly and with sufficient force, maximizing the chance of extinguishing the flames effectively. Each type of extinguisher may have different pressures suited for specific applications, but the principle of using pressure remains the same across all portable fire extinguishers.