Infrared spectroscopy has proven to be an excellent tool for identifying and quantifying gases, liquids and solid samples. For many applications, tunable laser based systems are displacing the traditional FTIR spectrometry, which utilizes black body radiators as the sources of broadband infrared radiation. Even though the laser-based systems are generally more expensive and not quite as versatile as the FTIR systems, they provide unique advantages of higher powers, better resolution, speed and a capability for projecting the interrogating light beam over long distances. Being able to project optical radiation over long distances provides infrared spectroscopy a special advantage over all other methods for detection and quantification of remote targets. All other techniques, including mass spectrometry require the instrumentation to be in close proximity of the target being interrogated. Of all laser based spectroscopy schemes, the mid wave infrared (MWIR) and long wave infrared (LWIR) regions have proven to be very effective for laser based systems, because most if not all relevant undesirable targets (gases, liquids and solids) have strong and well characterized absorption signatures in these regions and because, in general, MWIR and LWIR laser radiation is eye safe because of strong absorption by liquid water.