Ammonia: Is it safe?
Ammonia is one of the most efficient refrigerants known to man. It is non-flammable, readily available, and inexpensive to manufacture, making it ideal for large commercial refrigeration systems operating in industrial-type settings where it can be safely controlled and maintained by trained personnel. Using an ammonia-based refrigeration system does carry a certain risk factor, however. Let’s evaluate the pros and cons to determine whether this is the right application for your organization.
Pros of an ammonia-based system:
Ammonia has been used in refrigeration for 150-years
Ammonia is a naturally occurring substance. Composed of nitrogen and hydrogen, ammonia has a 150-year track record of use as a refrigerant on a commercial scale. Natural refrigerants like ammonia represent a return to the historical use of these gases.
The first recorded use of ammonia in refrigerant and cooling systems was in 1859. The natural refrigerant fell out of favor around 1920, partially in response to safety concerns and the rising popularity of synthetic alternatives.
Is ammonia environmentally friendly?
Ammonia is a natural substance and no special disposal procedures are required at the end of its life, unlike many other chemicals which are being phased out for these reasons. Unlike HFCs, which will be phased out by 2035, ammonia has a zero Ozone Depletion Level and zero Global Warming Potential rating.
Ammonia has better heat transfer properties than traditional refrigerants
Ammonia is slightly less efficient than some of the newer synthetic refrigerants but it has better heat transfer properties than most chemical refrigerants and allows for the use of equipment with a smaller heat transfer area thereby lowering the cost of constructing the system by 10-20%.
Here’s how it works: ammonia has a high heat capacity, absorbing about 600 Btu/lb to vaporize– which is about six times more than CO2 and synthetic refrigerants. This means ammonia refrigeration systems are much, much smaller than the equivalent alternatives. Its thermodynamic properties allow ammonia to be used as a refrigerant at relatively low pressures: between 100 and 150 psig.
Ammonia is inexpensive and widely available
In addition to its excellent thermodynamic properties, ammonia is generally considered nontoxic (read more below) and noncorrosive. It is also relatively inexpensive and readily available. As the cost of traditional refrigerants continues to increase, ammonia becomes a more enticing option.
Ammonia has a low failure rate in properly designed systems
The amount of ammonia required in a refrigeration system is very small compared to the size of the plant room and ducting. If a leak develops, it is easily detected due to the strong smell.
Safety concerns for ammonia-based systems
Is ammonia toxic?
Ammonia can be toxic in high concentrations. It is a corrosive gas with the potential of causing lung injury, and irritation or injury to eyes and skin when exposed at high levels. This can be mitigated in part by ammonia’s strong smell which acts as a safety valve and alerts of any leakage at 5PPM’s–which is well before concentrations considered to be dangerous occur–along with following the EPA-developed key safety measures for inspection of ammonia refrigeration systems.
Can ammonia catch on fire in refrigerant systems?
Ammonia is also flammable, but only under very specific conditions. Since ammonia is shipped and stored as a liquid, any release into the atmosphere will begin evaporating immediately, resulting in a rapid lowering of concentration below the flammable range. In terms of fires, ammonia has been shown to act as an excellent fire suppressant due to it being able to dilute oxygen levels significantly.
Ammonia is a natural product of animal waste and can be found in nature. Ammonia has been used as a refrigerant for decades. It is considered by many to be the most efficient refrigerant available. Refrigeration systems that use ammonia are generally more energy-efficient than other refrigerants, which translates into cost savings. In addition, ammonia systems are often designed with redundant systems that can automatically decrease/shut down leaks if detected through automation as well as double-walled piping, leak detection, and monitoring.