Pressure and density
When ammonia is subject to pressure or reaches very low temperatures, it turns into a clear liquid. When liquid ammonia is leaking, large quantities of ammonia gas are derived - 1 litre of liquid ammonia is derived into approx. 800 litres of ammonia gas. The pressure of the ammonia depends on the temperature:
- -5 ̊C: Pressure is 2,6 bar
- 5 ̊C: Pressure is 4,3 bar
- 15 ̊C Pressure is 6,4 bar
- 25 ̊C Pressure is 9,2 bar
The density of ammonia is also affected by temperature:
- -5 ̊C: Density is 0,645
- 5 ̊C: Density is 0,632
- 15 ̊C Density is 0,618
- 25 ̊C Density is 0,603
The colder it is, the more ammonia will be in the tank.
Ammonia/air mixtures are flammable, when they contain between 15% and 28% vol. ammonia gas (150,000-280,000 ppm). In extreme cases, the mixture will explode within these limits. However, ammonia is difficult to ignite in practice.
Ammonia gas, formed upon discharge from a tank, encompasses the risk of development of flammable concentrations.
Smoking and open flames forbidden when handling ammonia!
A severely boiling ammonia lake can burst into flames if ignited. However, such a fire will eventually end with the boiling. An ammonia lake, cooled down and resting due to heavy evaporation, will not desorb ammonia gas in quantities that can uphold an ammonia fire. A cold lake of liquid ammonia does therefore not encompass the risk of fire. Fire caused by i.e. leaking oil or gasoline is much more serious. Ignited ammonia generates water and nitrogen, and 79% of the atmospheric air is nitrogen.
Results from tests trying deliberately to ignite ammonia gas and liquid outside with a gas flame, where it is difficult to ignite ammonia, show that the fire will normally go out immediately after removing the gas flame. It is difficult to ”maintain” a flammable composition. Please note that these conditions will change if adding oil or gasoline. This means that it is difficult to make ammonia burn outside - however, exposure in closed rooms with explosive concentrations and a source of ignition may have fatal consequences.