Abstract: A calibration assembly generates elemental mercury and oxidized mercury for calibrating components of a mercury monitoring system, including making necessary adjustments to efficiencies of a mercury compound converter and an elemental mercury detector. The calibrator generates an elemental mercury sample having a known elemental mercury concentration, [Hg0]1 and combines an oxidizing component with the elemental mercury sample, thereby producing a reduced concentration of elemental mercury [Hg0]2 within the sample. The calibrator measures the concentration of elemental mercury [Hg0]2 within the sample and calculates a difference between the known elemental mercury concentration, [Hg0]1 and the reduced concentration [Hg0]2. The difference between [Hg0]1 and [Hg0]2 is substantially equal to the concentration of oxidized mercury produced by the calibrator.