A system (10) for delivery of dilute fluid, utilizing an active fluid source (12), a diluent fluid source (14), a fluid flow metering device (24) for dispensing of one of the active and diluent fluids, a mixer (38) arranged to mix the active and diluent fluids to form a diluted active fluid mixture, and a monitor (42) arranged to sense concentration of active fluid and/or diluent fluid in the diluted active fluid mixture, and responsively adjust the fluid flow metering device (24) to achieve a predetermined concentration of active fluid in the diluted active fluid mixture. A pressure controller (34) is arranged to control flow of the other of the active and diluent fluids so as to maintain a predetermined pressure of the diluted active fluid mixture dispensed from the system. The fluid dispensed from the system then can be adjustably controlled by a flow rate controller, e.g., a mass flow controller, to provide a desired flow to a fluid-utilizing unit, such as a semiconductor process tool. An end point monitoring assembly is also described, for switching fluid sources (12, 15) to maintain continuity of delivery of the diluted active fluid mixture.