An HF generator based on the dissociation pressure of an alkali bifluoride is described. Sodium bifluoride salt was found to yield HF pressures of the order of 0.001 to 0.3 mm in the temperature range 60 to 135 °C due to the equilibrium [Formula: see text]. The HF generator allows a dry carrier gas (typically N2) to pass through a thermoregulated chamber filled with the crystalline bifluoride and furnishes HF concentrations from 5 to 1000 ppm at flowrates up to 5 ℓ/min for periods up to one year. The HF concentrations thus generated were stable to within 1% after a 40 min warm up period. Described also is the associated control system which allows the operator to send alternately dry carrier gas with or without trace HF concentration to an external cell or analyser.