Fact Sheet: Ammonia (natural refrigerant)

Ammonia has been successfully used as a refrigerant in industrial refrigeration plants for over 130 years. It is a colourless gas, liquefies under pressure, and has a pungent odour. Ammonia has no ozone depletion potential (ODP = 0) and no direct global warming potential (GWP = 0). Thanks to its high energy efficiency, its contribution to the indirect global warming potential is also low. Ammonia is flammable and is toxic to skin and mucous membranes when highly pressurised. However, its ignition energy is 50 times higher than that of natural gas and ammonia will not burn without a supporting flame. Due to the high affinity of ammonia towards (air) humidity it is rated as "hardly flammable". Ammonia is toxic, but has a characteristic, sharp smell which makes a warning below concentrations of 3 mg/m³ ammonia in air possible. This means that ammonia is evident at levels far below those which endanger health. Furthermore ammonia is lighter than air and therefore rises quickly.

Appearance colorless
Odor distinctive, biting
Solubility in water (20 ºC, 1 bar) 0.517 kg or 650 l(g)/l water
Heat of solution 36 kJ/mol
Molecular weight 17.03 kg/kmol
Boiling point (1.013 bar) -33,3 ºC
Density of saturated vapour (20 ºC) 6.7025 kg/m³
Thermic decomposition > 450 ºC
Explosibility limits 15 Vol.-% to 34 Vol.-%
108,000 mg/m³
to 240,000 mg/m³
Ignition temperature 650 ºC
Ignition energy (20 ºC, 101 kPa) 14 mJ
Water content in the cycle of minor importance
Perception threshold 5 ppm 3,5 mg/m³
MAK-Value 50 ppm 35 mg/m³
Nuisance threshold 250 ppm 175 mg/m³
Tolerance threshold 500-1,000 ppm 350 -700 mg/m³
Signs of poisoning 2,500 ppm 1,750 mg/m³
Fatal dose > 5,000 ppm 3,500 mg/m³
Long-term effects not carcinogenic, not mutagenic
Concentration in human blood 0,8-1,7 ppm
Daily production in the human body 17 g ˜ 1 mol
Water hazard class 2, ID No. 211
Evaporation enthalpy at 0 ºC 1,262 kJ/kg
Vapor pressure at 0 ºC 4.29 bar
Compression ratio at 0 / 35 ºC 3.15
Volumetric refrigerating capacity
at 0 / 35 ºC
3,798.2 kJ/ m³
Isentropic refrigerating capacity number 0 / 35 ºC 6.75
Isentropic final compression temperature 0 / 35 ºC 82.6 ºC
Heat conductivity of the liquid
at 0 ºC
518.5 * 10-3 W/mK
Kinematic viscosity of the liquid
at 0 °C
2.66 * 10-7 m²/s
Heat transition (evaporation, condensation) Very high