What is the difference between stored-pressure and cartridge-operated extinguishers?

• A. Stored-pressure extinguishers have the propellant gas in the cylinder; cartridge-operated extinguishers use a separate cartridge to create pressure when discharged.
• B. There is no difference.
• C. The difference is not in how they store pressure.
• D. Stored-pressure is for indoor; cartridge for outdoor.

Answer: (A)

The main idea is how the pressure that drives the extinguisher is stored and released. In a stored-pressure extinguisher, the propellant gas is already inside the cylinder with the extinguishing agent. When you operate the handle, the valve opens and that internal gas pushes the agent out through the nozzle. In a cartridge-operated extinguisher, the gas that pressurizes the cylinder is kept in a separate cartridge inside the unit. When you discharge, the cartridge is ruptured, releasing the gas to pressurize the cylinder and expel the agent.

So the difference isn’t about indoor or outdoor use or about there being no difference; it’s about where the pressure comes from and how it’s released—inside the cylinder for stored-pressure, versus in a separate cartridge inside for cartridge-operated.