The JET Active Gas Handling System (AGHS) has been in operation in conjunction with the JET machine since Spring 1997. The tritium levels within the vessel have remained sufficiently high, 6.2g at the end of the DTE1 experiment and currently 1.5g, such that the AGHS has been required to operate continuously to detritiate gases liberated during D-D operations and to maintain discharges to the environment to ALARP. Maintaining the system to ensure continued operation has been a key factor in guaranteeing the continued availability of the essential sub-systems. The operational history of the JET AGHS has been previously documented in a number of papers. Operational downtime is minimised through well-engineered sub-systems that use high integrity components. Outage, contamination and operator dosage are minimised through pre-planned and prepared maintenance operations. The reliability of sub-system critical condition fault detection is demonstrated through routine testing of hard-wired alarms and interlocks.