Trace gas analyzers measure trace gas concentration in an air sample using tunable diode laser absorption spectroscopy. This technique provides high sensitivity, speed, and selectivity. It is a rugged, portable instrument designed for use in the field. The common applications of trace gas analyzers include gradient or eddy covariance flux measurements of methane or nitrous oxide and isotope ratio measurements of carbon dioxide or water vapor. It is ideally suited to measure fluxes of trace gases using micrometeorological techniques. Trace gas analyzers' sample rate, frequency response, sensitivity, and selectivity are optimized for measuring trace gas fluxes using the eddy covariance (EC) method.