Abstract: A fluorescent gas analyzer that provides a DC output signal that is proportional to the concentration of a given gas that fluoresces within a reaction cell over a predetermined interval is disclosed. The analyzer includes a detector combination and a compensation circuit that prevent the output signal from being affected by scattered excitation energy detected by the fluorescence detector or by variations in the excitation energy. The analyzer is particularly adapted for detecting fluorescence from SO.sub.2 that is excited by UV radiation.

Abstract: A mass exchange device and system that employs a semi-permeable diffusion barrier in the nature of a tubular membrane. A sample gas stream conduit is concentric with the tubular membrane, and the transport gas stream flows within the tubular membrane in a direction opposite to the flow of transport gas stream. Certain molecular species in the sample gas migrate across the tubular membrane and mix with the transport gas for passage to an analyzer. The conduit and tubular membranes are incorporated within a heat exchange cartridge and a heater and temperature controller maintain a desired temperature control of the system. Dual stream dilutions may be accomplished by sampling an exhaust gas prior to cleansing by a gas scrubber and also sampling the gas after cleansing. Both the upstream and downstream sample gases are diluted in a common heat exchange cartridge and passed to an analyzer.