The frequency of fire extinguisher checks and maintenance varies depending on the type of extinguisher and applicable regulations. Here's a general overview:

• Regular Inspection: Fire extinguishers should be inspected regularly. [1], [2], [3] The CAT excavator manuals recommend that you "Inspect the fire extinguisher and service the fire extinguisher regularly. Obey the recommendations on the instruction plate" [1], [2], [3]
• Weight and Pressure Checks: For refillable containers, the weight and pressure should be checked at least semi-annually. [4] If there's a loss of more than 5% in net content or weight, or a loss of more than 10% in pressure, maintenance is required [4]
• Non-Refillable Containers: Factory-charged non-refillable containers without pressure indicators should be weighed at least semi-annually, and replaced if there's a net weight loss of more than 5% [4]
• Internal Examinations: Dry chemical extinguishers in cylinder-operated systems should be examined annually [5]. Liquid charge-type AFFF and FFFP extinguishers should have their extinguishing agent replaced every 3 years, with an internal examination conducted at that time [5]. Solid charge-type AFFF extinguishers require agent replacement every 5 years during the hydrostatic test, along with a teardown [5]
• Hydrostatic Testing: Hydrostatic testing should be performed at intervals specified in relevant tables or when an extinguisher shows corrosion or physical damage [5].
• Six-Year Maintenance: Stored pressure extinguishers requiring a 12-year hydrostatic test should be emptied and undergo applicable maintenance every six years. [6]
• Nonrechargeable Extinguishers: Nonrechargeable extinguishers are good for 12 years from the date of manufacture and then must be taken out of service [5].

Always refer to the instruction plate on the fire extinguisher and obey the recommendations [1], [2], [3]. Also, consult local fire authorities for specific requirements [5].