A pungent alkaline gas, a compound of nitrogen and hydrogen (NH3). It is formed naturally when bacteria decompose nitrogen-containing compounds, such as manures. Emissions of ammonia can be a problem in enclosed livestock facilities, and in the ambient air they may contribute to very fine particulate matter. Synthetic ammonia is used as a nitrogen fertilizer. Also called anhydrous ammonia, it is the basic feed stock for the production of all nitrogen fertilisers as well as being a direct application material. Synthetic ammonia is made through a reaction between natural gas and nitrogen.