Characteristics of a Good Refrigerant

Refrigerants are substances that change from the liquid to the gaseous state to decrease the temperature of an appliance. This chemical process is used over and over again in refrigerators, air conditioners and other machines to keep the items inside consistently cool. Different refrigerants are used depending on the location, the type of machine and the application of items that are refrigerated.

Boiling Point

A substance used as a refrigerant should have a boiling point in a particular range that fits the machine in which it is used. A refrigerant with a lower boiling point tends to have a better ability to cool. Refrigerants with higher boiling points tend to be more efficient and may work well in a smaller machine. Most refrigerants have a boiling point between – 27.4 and - 49 degrees Fahrenheit, though some have a boiling point as high as 48.2 degrees Fahrenheit.

Lack of Toxicity

A refrigerant is classified as a Class A refrigerant if there is no toxicity identified in concentrations less than 400 parts per million. If there is toxicity identified in this small amount, the substance is a Class B refrigerant. Class 1 refrigerants are completely nonflammable, Class 2 types are moderately flammable and Class 3 substances are highly flammable. A good refrigerant has the right combination of safety and functionality. For example, in a regular home refrigerator, a Class A and Class 1 substance are used. In an industrial setting where more safety measures are in place and more refrigeration is needed, a Class B and Class 2 refrigerant are generally used.


Refrigerants must be stable substances that do not decompose under the pressures and temperatures of the refrigerator system. A less stable substance might swell, embrittle or dissolve the plastics used in the motor and seals of the system. The refrigerant should also not react chemically with the lubricants and other substances found in the refrigerator. Originally, chlorofluorocarbons (CFCs) were used as refrigerants until it was found that they were unstable when they came into contact with the ozone particles in the upper atmosphere.


A good refrigerant has no odor when it is in a low concentration so that the appliance does not have a chemical smell at all times. This refrigerant also has a distinct odor at higher concentrations so that when a device has chemical leaks, they can be quickly identified. Many refrigerants have an odor similar to carbon tetrachloride when they leak, which smells like chemicals used at the dry cleaners.