Gas detection system

The gas detection system provides for the effective detection of gas leaks over a large area. It includes a laser which has a laser line corresponding to an absorption line of the gas to be detected. A He-Xe laser scans a number of retroreflectors which are strategically located around a D2O plant to detect H2S leaks. The reflected beam is focused by a telescope, filtered, and passed into an infrared detector. The laser may be made to emit two frequencies, one of which corresponds with an H2S absorption line; or it may be modulated on and off the H2S absorption line. The relative amplitude of the absorbed light will be a measure of the H2S present