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ISO 817:2014 provides an unambiguous system for assigning designations to refrigerants. It also establishes a system for assigning a refrigerant safety classification based on toxicity and flammability data and provides a means of determining the refrigerant concentration limit.

The standard divides flammability into three defined classes with an additional subclassification:

  • Class 3: higher flammability.
  • Class 2: lower flammability.
  • Class 2L: lower burning velocity (BV) Class 2s with burning velocities less than or equal to 10 cm/s.
  • Class 1: no flame propagation.

Meanwhile, toxicity classification considers two classes (A and B), based on allowable occupational exposure:

  • Class A (lower chronic toxicity) refrigerant with an occupational exposure limit of 400ppm or greater.
  • Class B (higher chronic toxicity) refrigerant with an occupational exposure limit of less than 400ppm.

Historically, most refrigerants used in HVACR products were Class 1, or nonflammable – however most of these have high global warming potential (GWP) impact and are now being progressively replaced by a new generation of lower GWP gases. These gases, however, fall largely into the 2L class posing a flammability risk instead.

CO2 has a very promising future as a natural refrigerant with low environmental impact and safety concerns.

Ammonia, which falls in class B2L, has been used in large industrial refrigeration systems for a century. The safety of these systems is heavily controlled as the result of ammonia’s toxicity rather than its flammability.

Propane and other Hydrocarbons, which are Class 3 materials, have increasingly been used in small systems such as domestic refrigerators or freezers – normally with very small refrigerant charge sizes.

You can learn more about the use of these gases in one of our recent infographics.

Don’t forget to check what refrigerant gases can be detected with our comprehensive range of gas sensing solutions!

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