Safety Moment April: 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)
  • ·        Preambles to Final Rules
  • ·       Directives
  • ·       Standard Interpretations

National Consensus

  • American National Standards Institute (ANSI)/International Institute of Ammonia Refrigeration (IIAR)
  • American National Standards Institute (ANSI)/American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE)
  • American Society of Heating Refrigerating and Air-conditioning Engineers (ASHRAE)
  • American Society of Mechanical Engineers (ASME)
  • Compressed Gas Association (CGA)
  • FM Global
  • International Institute of Ammonia Refrigeration (IIAR)
  • IIAR Bulletins/Guidelines

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.

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.

Acknowledgement to OSHA: