6 YEAR MAINTENANCE 6 year maintenance is required for all extinguishers which are subject to the 12 year hydrostatic test this includes most stored-pressure extinguishers which can be recharged if the extinguisher passes the six year inspection, a label needs to be affixed to the unit stating that the extinguisher has been inspected. HYDROSTATIC TESTING Hydrostatic testing involves subjecting the fire extinguisher cylinder to pressures that exceed its rating to ensure it is still capable of maintaining the pressure necessary to discharge properly in the event of a fire. FIRE INSPECTOR A Fire Inspector visits and inspects buildings and other structures to search for fire hazards and to ensure that federal, state, and local fire codes are met they also test and inspect fire protection and fire extinguishing equipment to ensure they work.