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  • Ammonia Refrigeration. OSHA eTool. Assists employers and employees in identifying and controlling the hazards associated with the operation and maintenance of ammonia refrigeration systems. Many of the requirements of the Process Safety Management Standard, 29 CFR 1910.119, are identified in this eTool as possible controls, and are useful as recommended practices, whether or not the ammonia refrigeration system is a covered process.
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Ammonia Refrigeration

Ammonia is considered a high health hazard because it is corrosive to the skin, eyes, and lungs. Exposure to 300 parts per million (ppm) is immediately dangerous to life and health. Ammonia is also flammable at concentrations of approximately 15% to 28% by volume in air. When mixed with lubricating oils, its flammable concentration range is increased. It can explode if released in an enclosed space with a source of ignition present, or if a vessel containing anhydrous ammonia is exposed to fire. Fortunately, ammonia has a low odor threshold (20 ppm), so most people will seek relief at much lower concentrations.

Ammonia refrigeration is addressed in specific standards for the general industry.


This section highlights OSHA standards, preambles to final rules (background to final rules), directives (instructions for compliance officers), standard interpretations (official letters of interpretation of the standards), and national consensus standards related to ammonia refrigeration.

This section also contains a partial list of good engineering practices which may also apply to many ammonia refrigeration facilities. This list is not intended to be all-inclusive or definitive, but should provide employers with a starting point for finding applicable codes, standards, and guidelines.


Note: Twenty-five states, Puerto Rico and the Virgin Islands have OSHA-approved State Plans and have adopted their own standards and enforcement policies. For the most part, these States adopt standards that are identical to Federal OSHA. However, some States have adopted different standards applicable to this topic or may have different enforcement policies.

General Industry (29 CFR 1910)

  • 1910.38, Emergency action plans [related topic page]

  • 1910.119, Process safety management of highly hazardous chemicals. Applies to systems containing 10,000 lbs. of ammonia or greater. [related topic page]
    • Appendix A, List of highly hazardous chemicals, toxics and reactives (Mandatory)
    • Appendix B, Block flow diagram and simplified process flow diagram (Nonmandatory)
    • Appendix C, Compliance guidelines and recommendations for process safety management (Nonmandatory)
    • Appendix D, Sources of further information (Nonmandatory)
  • 1910.120, Hazardous waste operations and emergency response. Generally, the emergency response requirements of 29 CFR 1910.120(q) apply to employers who use refrigeration systems utilizing anhydrous ammonia as a cooling agent. [related topic page]
    • Appendix A, Personal protective equipment test methods
    • Appendix B, General description and discussion of the levels of protection and protective gear
    • Appendix C, Compliance guidelines
    • Appendix D, References
    • Appendix E, Training curriculum guidelines (Non-mandatory)
  • 1910.132, General requirements (Personal protective equipment) [related topic page]

  • 1910.133, Eye and face protection [related topic page]

  • 1910.134, Respiratory protection [related topic page]

  • 1910.138, Hand protection

  • 1910.307, Hazardous (classified) locations. There may be locations in an ammonia refrigeration system that are Class 1 Division 2 hazardous locations.

  • 1910.1200, Hazard communication. Employers are required to communicate the hazards associated with working with ammonia to appropriate employees. [related topic page]

Preambles to Final Rules


Standard Interpretations

National Consensus

Note: These are NOT OSHA regulations. However, they do provide guidance from their originating organizations related to worker protection.

American National Standards Institute (ANSI)/International Institute of Ammonia Refrigeration (IIAR)

  • 2-1999, American National Standard for Equipment, Design, and Installation of Ammonia Mechanical Refrigerating Systems. Guides the design, manufacture, installation, and use of ammonia mechanical refrigerating systems in industrial occupancies.

American National Standards Institute (ANSI)/American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE)

  • 15-2007, Safety Code for Mechanical Refrigeration. Promotes the safe design, construction, installation, and operation of refrigerating systems. Establishes reasonable safeguards of life, limb, health, and property; defines practices that are consistent with safety; and prescribes safety standards. The provisions of this code are not intended to apply to the use of water as a refrigerant.

  • 26-1996, Mechanical Refrigeration and Air-Conditioning Installations Aboard Ship. Provides recommendations and requirements for the safe and efficient design, construction, installation, operation, inspection, and maintenance of mechanical refrigeration equipment aboard ships.

American Society of Heating Refrigerating and Air-conditioning Engineers (ASHRAE)

  • 2006 Handbook - Refrigeration. Covers the refrigeration equipment and systems used for applications other than human comfort. Includes information on cooling, freezing, and storing food; industrial applications of refrigeration; and low-temperature refrigeration. Primarily a reference for the practicing engineer, but also a useful reference for anyone involved in the cooling and storage of food products.
    • Chapter 3, System Practices for Ammonia Refrigerant
    • Chapter 6, Control of Moisture and Other Contaminants in Refrigerant Systems

American Society of Mechanical Engineers (ASME)

  • B31.5-2001, Refrigeration Piping and Heat Transfer Components

  • Boiler and Pressure Vessel Code, 2007 Edition
    • Section V, Nondestructive Examination
    • Section VIII, Pressure Vessels

Compressed Gas Association (CGA)

  • G-2.1, American National Standard Safety Requirements for the Storage and Handling of Anhydrous Ammonia, (1999). Includes standards for the location, design, construction, and operation of anhydrous ammonia systems. Sections on refrigerated storage systems, systems mounted on farm vehicles, tank motor vehicles, and tank railcars for transportation purposes are included. This standard does not apply to ammonia manufacturing plants, or refrigerating or air conditioning systems.

FM Global

  • 7-13, Mechanical Refrigeration, (2007). Property Loss Prevention Data Sheet.

International Institute of Ammonia Refrigeration (IIAR)

  • Ammonia Data Book. Provides a variety of information on ammonia and includes a data on the various properties of ammonia and information on its use.

IIAR Bulletins/Guidelines

  • Suggested Safety and Operating Procedures When Making Refrigeration Plant Tie-Ins. No. 107-1997. Addresses the need to approach ammonia refrigeration system tie-ins in a safe and methodical manner. Provides owners and contractors with a general checklist of safety and logistical items that should be reviewed when planning system shutdowns and tie-ins. Provides engineers with ideas on how and where to design for future connections and taps that can make future tie-ins easier and safer.

  • Water Contamination in Ammonia Refrigeration Systems. No. 108-1986. Addresses the water contamination in ammonia refrigeration systems that has always been a problem, as owners typically know they have water in a system, but may not be familiar with how it got there; measures to quantify the amounts, analyzing the specific penalties it causes on the system performance; and removing the water in a safe manner. Offers insights on where the water can come from and how to minimize continued infiltration. Provides an analytical approach to quantifying water concentrations, and recommends apparatus to remove the water.

  • Minimum Safety Criteria for a Safe Ammonia Refrigeration System. No. 109-1997. Embraces an IIAR goal of ensuring that ammonia refrigeration systems are engineered, constructed and operated in a safe manner. Provides detailed lists of items to consider when designing, inspecting, or operating a system. Addresses such issues as housekeeping, record keeping, code considerations and personnel safety equipment. Provides inspection checklist forms for compressors, condensers, evaporators, vessels and heat exchangers to check system installation against recognized industry safety requirements.

  • Start-Up, Inspection and Maintenance of Ammonia Mechanical Refrigerating Systems. No. 110-1993. Covers ammonia characteristics and hazards, inspection and maintenance of equipment, start-up issues, reference standards, safety equipment, and log book record keeping. Provides definitions of system components and terms to help in understanding ammonia systems.

  • Ammonia Machinery Room Ventilation. No.111-2002. Provides a practical ventilation design criteria that will satisfy existing code requirements and improve machinery room safety. Major differences can be found between codes when determining ventilation requirements for ammonia machinery rooms. These differences result in confusion for the engineer and possible code misapplication.

  • Ammonia Machinery Room Design. No. 112-1998. Summarizes generally accepted industry practice for ammonia machinery rooms, and references relevant codes and standards where instructive. The recommendations in this guideline are most applicable to completely new ammonia machinery rooms. Application to the evaluation and/or renovation of existing machinery rooms may be impractical for a variety of reasons and should be done only with careful consideration.

  • Identification of Ammonia Refrigeration Piping and System Components. No. 114-1991. Provides a comprehensive ammonia labeling scheme for companies in need of an identification system that "covers it all." Offers recommendations on label sizes, colors, installation locations, and label material requirements.

  • Avoiding Component Failure in Industrial Refrigeration Systems Caused by Abnormal Pressure or Shock. No. 116-1992. Identifies three significant factors that can lead to ammonia refrigeration system damage and personnel injury: trapped liquid, sudden liquid deceleration, and vapor propelled liquid. Explains the most likely causes for each of these problems and provides design, operation and servicing tips that can minimize the chances of them occurring. Offers numerous suggestions on making hot gas defrost operations safer and more effective.

  • Process Safety Management Guidelines, (1998). Provides guidance on the interpretation and implementation of the OSHA Process Safety Management Standard. Contains a chapter discussing each of the fourteen elements and includes a series of work practices, checklists, and other guidance materials to assist employers in developing a process safety management program.

  • Risk Management Program Guidelines for Ammonia Refrigeration, (1998). Provides guidance on the interpretation and implementation of EPA's Risk Management Rule. A good companion to the Process Safety Management Guidelines manual also published by IIAR.

Recognition and Control

Anhydrous ammonia is widely used as a refrigerant in many industrial facilities, including:

  • Meat, poultry, and fish processing facilities

  • Dairy and ice cream plants

  • Wineries and breweries

  • Fruit juice, vegetable juice, and soft drink processing facilities

  • Cold storage warehouses

  • Other food processing facilities

  • Petrochemical facilities

Hazard Recognition

Ammonia spills and releases pose a significant threat to workers from skin contact, inhalation, and fire and explosion. The key provision of process safety management is process hazard analysis (PHA) - a careful review of what could go wrong and what safeguards must be implemented to prevent releases of hazardous chemicals. The following references help you to begin a PHA by recognizing process hazards.

  • Process Safety Management. OSHA Safety and Health Topics Page.

  • Ammonia. National Institute for Occupational Safety and Health (NIOSH), (1994, May). Provides an Immediately Dangerous to Life or Health Concentrations (IDLHs) document that includes acute toxicity data for ammonia.

  • Toxicological Profile for Ammonia. Agency for Toxic Substances and Disease Registry (ATSDR), (2004, September). Provides exposure risks, exposure limits, and health effects for ammonia.

  • ToxFAQs™ for Ammonia. Agency for Toxic Substances and Disease Registry (ATSDR), (2004, September). Answers the most frequently asked health questions about ammonia.

  • Public Health Statement for Ammonia. Agency for Toxic Substances and Disease Registry (ATSDR), (2004, September). Provides information on exposure risks, exposure limits, and health effects.

  • Ammonia [622 KB PDF, 6 pages]. New Jersey Department of Health and Senior Services, Hazardous Substance Fact Sheet, (2007, September). Provides a summary source of information of all potential and most severe health hazards that may result from ammonia exposure.

Worker Protection

Accidental releases of ammonia from refrigeration facilities have resulted in both injuries and deaths to employees of these facilities. These injuries and deaths are caused from contact with both liquid and vapor forms of ammonia. Because refrigeration systems operate at elevated pressures, additional care must be taken to maintain and operate these systems so as to prevent releases with potentially catastrophic consequences. OSHA has developed this page to assist employers in identifying and controlling the hazards associated with the operation and maintenance of ammonia refrigeration systems.

Case Studies

  • Report of Examination of Samples. OSHA, (1998, November 9). Provides a report describing galvanic corrosion found in an ammonia refrigeration pipe used near brine tanks. The pipe catastrophically failed, causing a release of ammonia and a subsequent explosion. The report illustrates the potential of corrosion of refrigeration piping used in similar service conditions.


An effective process safety management program requires a systematic approach to evaluating the whole chemical process. The following references aid in evaluating process hazards in the workplace.

  • Ammonia Refrigeration. OSHA eTool.
  • Additional Risk Management Program Guidance. Environmental Protection Agency (EPA).
    • General Risk Management Program Guidance. Contains an updated risk management program, which includes an appendix specifically addressing ammonia refrigeration facilities. While this guidance is primarily designed to assist with the development and implementation of a risk management plan as required by the EPA, much of the information can also be used by those who are required to comply with the OSHA Process Safety Management Standard (29 CFR 1910.119).
      • Appendix E: Supplemental Risk Management Program Guidance for Ammonia Refrigeration Facilities [378 KB PDF, 27 pages]. Note: This appendix replaces the former stand-alone document "Risk Management Program Guidance for Ammonia Refrigeration." This appendix is intended for facilities with ammonia refrigeration systems (e.g., food processors and distributors, refrigerated warehouses). It covers only anhydrous ammonia and provides offsite consequence analyses that are specific to the ways in which ammonia is handled in an ammonia refrigeration system.
  • Model Risk Management Program and Plan for Ammonia Refrigeration [456 KB PDF, 78 pages]. Environmental Protection Agency (EPA), (1996, May). Helps owners and operators of ammonia refrigeration facilities comply with the OSHA Process Safety Management Standard (29 CFR 1910.119) and EPA's General Risk Management Program Guidance (40 CFR Part 68). Specific guidance is given on how to perform the Hazard Assessment, and the requirement for a Management System, Prevention Program, and Emergency Response Plan. Also included is a brief report of past accidental releases of ammonia and their root causes from EPA's Accidental Release Information Program (ARIP) database.

Additional Information

  • About CGA. Compressed Gas Association (CGA).

  • American Society of Mechanical Engineers (ASME)

  • Committee Operations. American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE).

  • Educational Materials. Refrigerating Engineers and Technicians Association (RETA).

  • In-depth Files. International Institute of Refrigeration (IIR).

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