Because of its many uses, ammonia (NH3) is one of the most highly produced inorganic chemicals worldwide. It is used in the petroleum industry to neutralize the acids in crude oil to protect equipment from corrosion and by natural gas plants as a method of NOx control. Ammonia is also used as a refrigerant in industrial refrigeration systems found in food and beverage facilities and by the fertilizer industry to produce ammonium and nitrate salts. Despite its wide application, NH3 is caustic and hazardous, with exposure to high concentrations leading to lung damage and death. Exposure to gaseous ammonia is limited by the American Conference of Governmental Industrial Hygienists (ACGIH) to 15 minutes at 35 ppm and 8 hours at 25 ppm.