The sample, whether coming directly from the bulkhead or processed within the converter, then flows through a hydrocarbon kicker. The kicker removes hydrocarbons from the sample by forcing the hydrocarbon molecules to differentially permeate through the tube wall. The SO2 molecules undergo the hydrocarbon kicker unaffected.
The sample then flows into the fluorescence chamber, where pulsating UV light excites the SO2 molecules. The condensing lens focuses the pulsating UV light into the mirror assembly. The mirror assembly contains four selective mirrors that reflect only the wavelengths which excite SO2 molecules.
As the excited SO2 molecules decay to lower energy states they emit UV light that's proportional to the SO2 concentration. The bandpass filter allows only the wavelengths emitted by the excited SO2 molecules to succeed in the photomultiplier tube (PMT). The PMT detects the UV light emission from the decaying SO2 molecules. The photodetector, located at the rear of the fluorescence chamber, continuously monitors the pulsating UV light and is connected to a circuit that compensates for fluctuations within the UV light.
As the sample leaves the optical chamber, it passes through a flow sensor, a capillary, and therefore the shell side of the hydrocarbon kicker. The SO2 gas analyzer outputs the SO2 ranges concentration levels to the display.