Ammonia

Facts about ammonia

• Chemical denotation: NH3

• Density at 20 ̊C: 0.61

• Freezing point: -78 ̊C

• Boiling point: -33 ̊C

• Ignition temperature: 650 ̊C

• Explosion limit: 15% -28% vol.

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Ammonia is used for production of many things that most of us use in our everyday life, for instance cleaning products, medicine, cosmetics, packaging and yeast. It is further used in the production of fertiliser, as liquid fertiliser and as coolant in for instance air conditioning systems.

Safety

Ammonia should be handled with utmost respect. When handling ammonia, you should always wear protective clothing, safety gloves and safety goggles, as well as respiratory protection and have access to eye rinsing solution on site. If handling ammonia outside, you should be aware of the wind direction in order to escape any potential leak. A leak is quite easy to detect due to the distinct smell, which can be smelled long before the concentration is hazardous to inhale. 

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The National Safety Council in USA has set the following concentration for the physical effects of ammonia (1 ppm = 1:1000000, which is 0.00071 grams of ammonia per square metre air):

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• ​​20 ppm: First noticeable smell
• ​40 ppm: Some people may experience eye irritation
• ​100 ppm: Clear eye and nose irritation after few minutes of exposure
• ​400 ppm: Severe irritation of the throat, nose and respiratory system
• ​700 ppm: Severe eye irritation. No permanent disablement if exposure is less than 30 minutes
• ​1700 ppm: Critical coughing – bronchial cramp – exposure less than 30 minutes can be lethal
• ​5000 ppm: The concentration is lethal almost immediately

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The hygienic limit value (HGH) is 20 ppm, corresponding to the concentration that the time weighted average of concentration should not exceed during a work day.

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:

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• -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

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The density of ammonia is also affected by temperature:

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• -5 ̊C: Density is 0,645
• 5 ̊C: Density is 0,632
• 15 ̊C Density is 0,618
• 25 ̊C Density is 0,603

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The colder it is, the more ammonia will be in the tank.​

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Fire hazard

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.

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Ammonia gas, formed upon discharge from a tank, encompasses the risk of development of flammable concentrations.

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Smoking and open flames forbidden when handling ammonia!

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​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.

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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. ​