Which type of fire extinguisher contains both the extinguishing agent and expellant in the same shell?

Stored pressure fire extinguishers contain both the extinguishing agent and the expellant within a single shell. This design allows the extinguisher to be ready for immediate use, as the agent is pressurized and can be discharged quickly when the nozzle is activated. These extinguishers are common for various applications because they are generally easier to operate and maintain. The stored pressure mechanism means that they rely on the pressure of the gas within the same container to propel the extinguishing agent out when needed, ensuring a straightforward and efficient response to a fire.

In contrast, cartridge-operated fire extinguishers use a separate cartridge filled with gas, which must be punctured to release the propellant, adding a layer of complexity. Hand-held fire extinguishers simply refer to the portable size of the device without specifying the mechanism of operation, and water-based fire extinguishers describe the agent used but do not indicate how it is stored or expelled.