How many basic designs are there for handheld dry chemical extinguishers?

Handheld dry chemical extinguishers typically come in two basic designs: stored pressure and cartridge-operated.

In the stored pressure design, the extinguishing agent and the propellant gas are combined in the same chamber, which allows for immediate discharge when the nozzle is activated. This design is straightforward and commonly used in many portable extinguishers.

The cartridge-operated design has a separate cartridge containing the propellant gas, which is released into the extinguisher to expel the dry chemical agent. This design can be advantageous in providing a more controlled discharge and can allow for easier maintenance, as the propellant can be replaced independently from the chemical agent.

Being aware of these two fundamental designs helps firefighters and first responders choose the appropriate extinguisher for different situations and understand their operation better.