The MultiGas™ TFS™ Monitor is an online, multi-compound, trace gas monitoring system in a stand-alone 19-inch rack enclosure. It uses an innovative tunable filter spectroscopy technology enabling high selectivity and stability measurement. Low detection limit (sub-ppm levels for most gases) is achieved through the use of high throughput optics coupled with a long-path gas cell and a high sensitivity detector. The all-optical MultiGas TFS Monitor provides an alternative to the traditional analyzer technologies for trace hydrocarbon, moisture, CO, CO2 and N2O measurements, enabling low cost yet high performance analysis. The analyzer is permanently calibrated, reducing the need for costly reference gas mixtures. The calibration stability is guaranteed through the use of "feature based" measurement and an advanced spectral processing algorithm that compensates for baseline variations.