What is an OP FTIR?

An Open-Path FTIR (Fourier-Transform Infrared) is a sophisticated instrument package that allows real-time, continuous measurement of a broad range of volatile organic and inorganic compounds.  OP-FTIRs are based on infrared spectrometers used in chemical labs since the 1960s.  However, FTIR technology as a field application to measure airborne chemical levels is relatively new since the early 1990s.  FTIR monitors provide both qualitative and quantitative information; which means they identify the compounds present and also calculate the concentration of each.  FTIR monitors received the official endorsement of the Environmental Protection Agency in 1998 when it published EPA Standard Method TO-16, in which EPA recommends FTIR as the best technology for measuring airborne pollutants in residential areas.   The “Open-Path” designation means that the infrared light source and detector are both contained in the same instrument.  This allows the infrared beam to be directed over variable distances and directions to a retro-reflector that returns the beam to the monitor.  The actual distance measured is therefore twice the distance separating the FTIR monitor and the reflector.  This feature also allows the reflector to be easily repositioned to measure volatile pollutants in other directions and over varying distances.   Thus, FTIR monitors are suitable for field applications, such as in residential areas near the Intel manufacturing plant in Rio Rancho, New Mexico, where nearby community members have had concerns about gaseous toxic chemical releases from the Intel plant.  FTIR monitors are likewise suitable for monitoring toxic chemicals in the vicinity of other Intel facilities, such as those in Chandler, Arizona and Beaverton, Oregon where volatile organic and/or inorganic compounds are released.     FTIR monitors can measure nearly all volatile compounds, except for diatomic molecules of the same element, such as chlorine and fluorine.  Essentially all other volatile chemicals, including organo-metallic compounds will be detectable if they are gases.  Other volatile acids such as hydrogen chloride (HCl) and hydrogen fluoride (HF) will be detectable if Intel is releasing them.  A significant portion of Intel's emissions are volatile organic compounds (VOCs), of which Intel may be emitting more compounds and higher volumes than those it reports to the New Mexico Environment Department.     FTIR monitors measure only gaseous compounds, and thus cannot measure particulate matter (soot, smoke, dust, etc.)  Nonetheless, the FTIR monitors serve as a potent tool for identifying what gaseous organic and inorganic chemicals Intel is releasing and what their concentrations are in the ambient air.    The FTIR detection limits for most of the organic chemicals emitted from Intel are in the low parts-per-billion range, which is excellent for a continuous, real-time monitoring system.  When nearby residents can smell Intel's emissions, as they report, the concentrations probably range from the high parts per billion levels to low parts per million.   The FTIR monitor will detect most of the chemicals being emitted by Intel when the wind is blowing from the plant's stacks/vents toward the FTIR monitoring path.  Because the FTIR monitor includes a weather station, each measurement incorporates the wind speed and wind direction at that time. This combination of weather data and detected compounds makes it relatively easy to identify the most probable source of the emissions.

One of the CRCAW members is retrieving collected data from FTIR. Front view of FTIR Side view of FTIR   Front view of Retro-Reflector, which allows it to return the reflected beam to its exact point of origin.