How does an NDIR gas analyzer work?

NDIR (Non-Dispersive Infrared) analyzers measure gas concentration by absorption of infrared radiation at specific wavelengths. Components: IR source, sample cell, reference cell, optical filter (selects target gas wavelength), and detector. Gas molecules absorb IR at characteristic wavelengths; detector compares sample and reference to determine concentration. NDIR is commonly used for CO, CO2, and hydrocarbons. Benefits: selective, stable, no consumables. Considerations: interference from other gases, zero drift, and proper sample conditioning.