After the cartridge is punctured on a cartridge-operated extinguisher, how is the discharge controlled?
- By squeezing a lever on top of the valve on the agent shell
- By turning the cartridge to open or close it
- By tilting the shell forward or backward
- By squeezing the shutoff nozzle at the end of the hose
Show the answer
D. By squeezing the shutoff nozzle at the end of the hose
The cartridge charges the shell and hose, and the operator starts and stops the flow at the hose nozzle. There is no squeeze-grip valve on the shell as there is on a stored-pressure unit.
Reference: NFPA 10: extinguisher types and operation
Why do many heavy industrial sites prefer cartridge-operated dry chemical extinguishers?
- They never need a hydrostatic test of the shell
- They can be refilled on site quickly after use
- They hold pressure longer once they are charged
- They are lighter than stored-pressure units of the same rating
Show the answer
B. They can be refilled on site quickly after use
Because the shell is not pressurized in storage, trained plant staff can refill agent and fit a fresh cartridge right after use, and the rugged shells suit frequent use. The shells still need periodic hydrostatic testing.
Reference: NFPA 10: extinguisher types and operation
A cartridge-operated extinguisher has no pressure gauge. How is its readiness verified during maintenance?
- Weigh the cartridge and check the agent level and condition
- Tap the shell and listen for a full sound
- Puncture the cartridge briefly and reseal it with a new disc
- Read the pressure at the hose nozzle
Show the answer
A. Weigh the cartridge and check the agent level and condition
The gas cartridge is weighed against the weight stamped on it and the dry chemical is checked for correct fill and free flow. The shell is at atmospheric pressure, so there is nothing for a gauge to read.
Reference: NFPA 10: maintenance of cartridge-operated extinguishers