Tunable diode laser absorption spectroscopy (TDLAS, sometimes referred to as TDLS, TLS or TLAS[1]) is a technique for measuring the concentration of certain species such as methane, water vapor and many more, in a gaseous mixture using tunable diode lasers and laser absorption spectrometry. The advantage of TDLAS over other techniques for concentration measurement is its ability to achieve very low detection limits (of the order of ppb). Apart from concentration, it is also possible to determine the temperature, pressure, velocity and mass flux of the gas under observation.[2][3] TDLAS is by far the most common laser based absorption technique for quantitative assessments of species in gas phase.