Ammonia has the chemical formula of NH3 and is a popular chemical used in many applications. One of the common industrial uses for ammonia is as a refrigerant. When used as a refrigerant, ammonia is very pure (99.98% pure) compared to ammonia that people may have in their homes, which is mixed with water to be 5-10% pure. Ammonia used in industry is often referred to as anhydrous ammonia, which means it doesn’t contain water.
Hazards of Ammonia
When using ammonia refrigeration, or ammonia for anything in the workplace, there are a variety of OSHA regulations that need to be followed. Having proper safety equipment in place and keeping the refrigeration unit well maintained can help reduce the risk to employees.
Ammonia can be very dangerous. If someone is exposed to as little as 300 parts per million in the air around them, they will experience extreme health issues and potentially even death. Direct contact with ammonia is also corrosive to humans. If ammonia gets on someone’s skin or eyes, it must be washed off immediately and treated right away to prevent long-term problems.
OSHA provides guidance for handling ammonia emergencies, as well as first aid recommendations.
Fortunately, ammonia has a very strong odor that people naturally find offensive. This odor is very distinctive and detectable at around 20 parts per million, which is significantly lower than the hazardous levels. When people begin smelling ammonia, they can evacuate the area quickly and have the maintenance teams take care of the problem.
Ammonia is also quite flammable. If there is a 15% or higher concentration in the air, it can ignite when exposed to an ignition source. In ammonia refrigeration, the ammonia is often mixed with lubricating oils, which can cause it to become even more flammable. Having fire suppression systems in place around ammonia refrigeration units is often recommended.
Advantages of Ammonia Refrigeration
When proper precautions are taken, ammonia refrigeration units offer many advantages compared to traditional CFC or HCFC based units. For many large industrial situations, these advantages make this type of refrigeration unit a smart choice:
- Less Expensive – Ammonia refrigerators require narrower piping, which is cheaper to make. This type of refrigeration unit will cost 10-20% less than other models.
- Efficient – Ammonia refrigeration is also 3-10% more efficient to run than units that use CFCs. This translates to lower electric bills and a facility that is more environmentally friendly.
- Ozone Safe – Unlike CFCs, ammonia does not harm the ozone layer. Experts also agree that ammonia use in refrigeration does not contribute to global warming.
- Chemical Cost – Ammonia is significantly cheaper to obtain and use than CFCs, which makes it more affordable to "recharge" a unit.
Whenever working with ammonia refrigeration units, it is important to remember that ammonia can be corrosive to certain types of metals. Copper piping, which is commonly used in other types of refrigeration units, cannot be used when working with ammonia.
Labeling the piping in these units to alert those performing maintenance to this requirement can help avoid potential problems. If this precaution is not taken, someone may unintentionally replace a pipe with one made of copper, leaving the facility at risk of a leak.
International Institute of Ammonia Refrigeration (IIAR) Bulletins
The International Institute of Ammonia Refrigeration is an organization that educates and informs about best practices for safely using ammonia for refrigeration. IIAR also provides standards for this purpose.
Additionally, IIAR publishes bulletins that offer guidance to facilities. This guidance provides clarification about safe ammonia use, especially when standards do not explain a particular topic. Below are relevant bulletins:
IIAR Bulletin 108 – Guidelines for: Water Contamination in Ammonia Refrigeration Systems
- Explains how water can contaminate an ammonia refrigeration system, how this can be prevented, and how water can be removed.
IIAR Bulletin 109 – Guidelines for: IIAR Minimum Safety Criteria for a Safe Ammonia Refrigeration System
- Covers the safe design, operation, and inspection of ammonia refrigeration systems. Also includes ammonia refrigeration safety inspection checklists for equipment.
IIAR Bulletin 110 – Guidelines for: Start-Up, Inspections and Maintenance of Ammonia Mechanical Refrigerating Systems
- Covers ammonia hazards as well as equipment maintenance and start-up issues.
IIAR Bulletin 114 – Guidelines for: Identification of Ammonia Refrigeration Piping and System Components
- Provides ammonia labeling guidelines that cover label materials, sizes, colors, etc.
Ammonia Pipe Labeling Requirements
As mentioned above, IIAR Bulletin 114 covers the requirements for ammonia piping labels. These requirements are different from ANSI pipe label guidelines, which apply to most other pipes and are accepted by OSHA in its pipe labeling requirements as well.
IIAR’s guidelines explain that ammonia marking labels must meet specific requirements for content and formatting.
Labels have five parts: abbreviations for ammonia system components, physical state (liquid/vapor), marker body (“AMMONIA”), the pressure level (low/high), and an arrow indicating the flow direction.
Ammonia Pipe Abbreviations
IIAR Bulletin 14 includes a list of abbreviations that can appear on an ammonia pipe label such as: CD (Condenser Drain), LT (Liquid Transfer), LTRS (Low Temperature Recirculated Suction, OD (Oil Drain), and RV (Relief Vent). Users can consult IIAR for a full list of accepted abbreviations.
Ammonia Piping Color Code
Recent updates to IIAR Bulletin 114 require that ammonia pipe labels are orange with black text (they were previously yellow). The physical state Liquid should be on a yellow rectangle, and Vapor should be on a blue rectangle. The pressure Low should be on a green rectangle, and High should be on a red rectangle. Consult the diagram above for placement of these label parts.
Those interested can also learn more about these industrial labeling requirements in our Ammonia Pipe Marking Guide, which explains how to create labels according to IIAR pipe marking guidelines.
Ammonia Process Safety Management
Businesses that use ammonia for refrigeration and have systems that contain 10,000+ pounds of ammonia (about 2000 gallons, according to the EPA) should also consult guidelines for process safety management. OSHA’s standards can be found here. OSHA’s Ammonia Refrigeration eTool also has information about IIAR Process Safety Management Guidelines for Ammonia Refrigeration.
Process safety management deals with how to safely manage processes that use hazardous chemicals, and ammonia falls into this category of very hazardous chemicals.