The functional requirements for fixed tritium in air monitors at CANDU nuclear facilities have recently been revised. The new requirements take into account new facility design, operating experience with monitors, and the need to provide a cost-effective monitoring strategy based on the complementary use of different instrument types. A set of performance requirements for the fixed monitors have been derived which address those characteristics which have a direct bearing on the level of radiation protection provided. To satisfy these performance requirements area-dedicated monitors will be used; i.e. one instrument for each area to be monitored, rather than the centralized multi-area monitoring systems previously employed.