Abstract: The concentration of multiple polyatomic gases are determined simultaneously by Raman light scattering. The gas sample is placed in a sampling cell and a polarized laser beam is passed through the cell, along a longitudinal axis. A portion of the light scattered by the gas sample is captured and detected by means of multiple collection optics-filter-detector channels. The scattered light exits the gas cell via windows located in the sides of the gas cell and enters the collection channels which are aligned with the cell windows. The cell windows are along the longitudinal axis of the laser beam and gas cell. Light scattered by the gas sample provides signals of both inelastic Raman scattered light and elastic laser scattered light which are directed to the collection channels. The optics of each channel transports the scattered light signals onto a laser line rejection filter where the elastic scattered laser signals are attenuated.