The provisions of the fire precautions (Workplace) Regulations  Regulation 6 require that "where it is necessary to provide extinguishing equipment to safeguard employees in the event of the fire, this equipment shall be maintained in an efficient state, in efficient working order and in good repair."
Inspections should include checks that each extinguisher:
Is located in the designated place;
Is unobstructed, visible and its operating instructions face outwards;
Has operating instructions which are clean and legible;
Is not obviously damaged;
Has a reading in the operable range or position of any pressure gauge or indicator fitted;
Has seals and tamper indicators which are not broken or missing.
Maintenance should be carried out by a competent person (usually a specialist contractor) 12 months after installation of a new extinguisher, and at 12 monthly intervals thereafter. The following chart shows the basic types & frequency of maintenance:
Extinguisher Type Basic Service Extended Service Overhaul & Recharge
Water & Foam Annually 5 Yearly
Powder Annually 5 Yearly
CO2 Annually 10 yearly