How does Tunable Diode Laser Absorption Spectroscopy (TDLAS) work for gas analysis?

TDLAS uses narrow-linewidth laser tuned across specific gas absorption line. Laser wavelength modulated rapidly; absorption at characteristic wavelength indicates concentration per Beer-Lambert law. Configuration: extractive (flow cell with laser and detector) or in-situ (cross-duct, path-length up to 20m). Advantages: high specificity (one absorption line per laser), fast response (<1 second), low detection limits, and minimal cross-interference. Applications: moisture in gases (ppb-ppm), O2, HCl, HF, NH3, and process gases. Wavelength Modulation Spectroscopy (WMS) provides improved sensitivity. Consider: laser selection for target gas, path length optimization, and pressure/temperature compensation.