Disclosed are a system and method for monitoring total mercury within a
gas sample in a substantially continuous manner and for calibrating for
both elemental and oxidized mercury. A converter of the Continuous
Emission Monitoring System (CEMS) receives a gas sample containing
vaporized mercury from a probe. The converter converts oxidized mercury
present within the gas sample into an elemental mercury component and an
oxidizing component using thermal cracking. The converter also reduces
the pressure of the gas sample to minimize recombination of the elemental
mercury component with the oxidizing components. A mercury analyzer of
the system receives the reduced pressure gas sample from the converter
and detects the fluorescence of the elemental mercury within the sample.
The mercury analyzer holds the gas sample at the reduced pressure to
reduce an effect of fluorescence quenching on the fluorescence of the
elemental mercury within the sample and provides substantially accurate
measurement of the concentration of the elemental mercury in the gas
sample.