Ammonia is a colourless gas with a sharp, penetrating, intensely irritating odour and a colourless liquid under pressure. It is not considered a flammable gas but a large and intense energy source may cause ignition and/or explosion. Ammonia gas can decompose at high temperatures forming very flammable hydrogen and toxic nitrogen dioxide. It is a COMPRESSED GAS and a confined space explosion and toxicity hazard. Ammonia gas is a CORROSIVE GAS and may be fatal if inhaled. Ammonia gas causes lung injury--effects may be delayed. The liquefied gas can cause frostbite and corrosive injury to eyes and skin.

The primary use of ammonia gas is in the fertilizer industry, as a direct application fertilizer and as a building block for the manufacture of nitrogen fertilizers, such as urea, ammonium nitrate, ammonium sulfate, ammonium phosphate and nitrogen fertilizer solutions. It is also used in production of nitric acid and in the fibres and plastics industry for the production of caprolactam, acrylonitrile, hexamethylenediamine, toluene 2,4-isocyanate and melamine.

Less important uses include the manufacture of explosives; as a refrigerant in both compression and absorption systems; in the pulp and paper industry; in metal-treating operations, such as the nitriding of steels and bright annealing; in the extraction of certain metals, such as copper, nickel and molybdenum from their ores; in pH control; removal of nitrogen oxides and sulfur oxides from stack gases; as a corrosion inhibitor at petroleum refineries and natural gas plants; in the rubber industry for the stabilization of natural and synthetic latex; in the food and beverage industry; as a curing agent in making leather; manufacture of moth proofing; in the manufacture of pharmaceuticals, dentifrices, lotions and cosmetics; in the manufacture of household ammonia, detergents and cleaners; in combination with chlorine to purify industrial and municipal water supplies; in the manufacture of numerous organic and inorganic chemicals, such as cyanides, amides and dye intermediates; and as a precipitant in uranium concentrate production.

It is a normally found in the body as a by-product of protein and nucleic acid metabolism, and is a minor component of the diet.

Ammonia gas is commercially available in a number of grades depending on its intended use, such as agricultural, refrigeration, metallurgical and electronic grades, with a minimum purity of 99.5%. Ammonia is shipped and stored as a liquefied gas under its own vapour pressure (787 kPa at 21.1 deg C). Ammonia is also available in water solution. Solutions of less than 25-30% have specific hazards and control measures which are reviewed in the chemical profile record for ammonium hydroxide. Solutions of greater than 25-30% readily give off ammonia gas at normal temperatures. Therefore, the information in this review applies to these more concentrated solutions.

Ammonia gas is also known as anhydrous ammonia, ammonia, and as ammoniac in French.

Its CAS Registry Number is 7664-41-7. This number is assigned by the Chemical Abstracts Service (CAS) in the United States and is used as a unique identifier number world-wide.