Abstract: An apparatus for detecting the presence of polycyclic aromatic hydrocarbons in the effluent of a turbulent commercial combustion system for monitoring or controlling the composition of the effluent. The apparatus is a system for directyl selectively detecting the presence in the effluent high molecular weight polycyclic aromatic compounds having five or more rings by laser induced fluorescence. The system includes an illuminating source of select fluorescence excitation of wavelengths that induces substantial fluorescence by high molecular weight polycyclic aromatic hydrocarbons in the gas phase.

Abstract: Detecting the presence of PAC's in the effluent of a combustions system by detecting the presence of a high molecular weight PAC's having five or more rings. A position along the effluent stream is selected at which high molecular weight PAC's may be present. The effluent is illuminated with radiation having a wavelength absorbed by the high molecular weight PAC's in the gas phase. The fluorescence from the illuminated effluent is detected, and analyzed by comparison to the known fluorescence of high molecular weight PAC's in the gas phase to determine the presence of the PAC's in the effluent. The effluent composition may be controlled in response to the detection.