“Over the past five years, over 120 open-path analyzers (along with dozens of meteorological and point monitors for other compounds) have been installed and operated at the fenceline of several large oil refineries in California. Similar programs exist in other states or are under consideration. The open-path monitor types employed include UV-DOAS, FT-IR, and TDL, depending on the target species and site characteristics. These analyzers measure many key pollutants defined by regulatory or other site requirements at detection limits appropriate for the specified health-based standards.”