Anhydrous ammonia is used extensively throughout the United States for a variety of purposes. We find ammonia in agriculture, in the manufacture of synthetic fibers, plastics and explosives, in refrigeration plants, and in the manufacture of ammonium compound containing fertilizers. We also find ammonia in common household cleaners, metallurgical processes, and in power plants for emissions controls. Approximately eighty percent of manufactured ammonia is used for agricultural purposes, either as a direct application of anhydrous ammonia (about 33% of the total), application of an ammonium solution (e.g. ammonium hydroxide or aqua ammonia), or as a dry fertilizer product. Ammonia is a naturally occurring colorless gas that is an inhalation hazard and has an extremely pungent odor; the odor threshold for ammonia vapor is between five and fifty parts per million (ppm). It is estimated that some 140 million metric tons are produced annually by commercial means, and that this total is approximately equal to the amount produced naturally. The preponderance of naturally occurring ammonia is derived from decomposing animal excreta with the decay of organic materials (plants, dead animals, etc.) providing the balance.
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