Types of Gas Detectors: (2) Infrared Point Detectors: Infrared point sensor Infrared (IR) point sensors use radiation passing through a volume of gas to detect leaks. Energy from the radiation is absorbed as it passes through the gas at certain wavelengths. The range of wavelengths that is absorbed depends on the properties of the specific gas. Carbon monoxide absorbs wavelengths of about 4. 2-4. 5 μm, for example. This is approximately a factor of 10 larger than the wavelength of visible light, which ranges from. 39 μm to. 75 μm for most people. The energy in this wavelength is compared to a wavelength outside of the absorption range; the difference in energy between these two wavelengths is proportional to the concentration of gas present. This type of sensor is advantageous because it does not have to be placed in the gas itself in order to detect it. Infrared point sensors can be used to detect hydrocarbons, compounds composed of hydrogen and carbon atoms, and other infrared active gases such as water vapor and calcium fluoride. IR sensors are commonly found in wastewater treatment facilities, refineries, gas turbines, chemical plants, and other facilities where flammable gases are present and the possibility of an explosion exists. Engine emissions are another area where IR sensors are being researched for use. The sensor would be able to detect high levels of carbon dioxide in the vehicles’ exhaust, and even be integrated with the vehicles’ electronic systems to notify drivers