The quantitative analysis of complex gas mixtures, such as the hydrazines and their air oxidation products, is of paramount importance in closed cycle systems used, for example, in submarines. A laser optoacoustic (photoacoustic) spectrometer which is capable of detecting these species at parts per billion levels has been developed and a system for field use is described. Laser optoacoustic measurements have been made on a range of other species which absorb in the CO2 laser region of 9 - 11.3~m, including many atmospheric pollutants such as the chlorofluorocarbons, perfluorocarbons, and some of the new 'ozone friendly' propellant and refrigerant species. Absorption coefficient data and limits of detection have been established for many gaseous molecules, and a series of optoacoustic cells has been designed, together with a novel method for the generation of gaseous species at low concentrations. A CO2 laser based optoacoustic spectrometer is compared favourably with a range of other current methods used to detect low levels of atmospheric contaminants, and has been shown to be a most suitable technique for the quantitative detection of a wide range of substances at the parts per billion level.