Maintenance of pressurized fire extinguishers
The extinguisher should be inspected at regular intervals (monthly or more often if circumstances dictate) to insure that it is ready for use. Inspect that a fire extinguisher is available and is in operating condition. It is intended to give reasonable assurance that the fire extinguisher is fully charged.
Visually inspect the pressure gauge:
a. If bent, damaged or improper gauge, depressurize and replace.
b. If pressure is low, check for leaks.
c. If over pressurized (overcharged), depressurize the extinguisher and follow recharge instructions.