The next time you buy some refrigerant, be sure to check the expiration date on the can or cylinder.
What? You can’t find one?
That’s because refrigerant simply does not go bad or expire. As long as the cylinder or can is fully sealed (no leaks) and the valve is not open or broken, refrigerant will last in its container indefinitely. If intact, the can/cylinder is a sealed unit and will not deplete or leak refrigerant.
The same is true of refrigerant in your A/C system. Like the can or cylinder, the system is a self-contained closed loop which contains refrigerant. As the refrigerant continuously moves through the system, it changes phases from liquid to gas, absorbing and releasing heat as it does so. Again, the refrigerant will not go bad, nor will it ever be “used up”. The only time refrigerant needs to be added is if there was an initial “undercharge” during installation, or if there is a leak, either from a collision or a defect in a component of the system. Therefore, not only does refrigerant not “go bad”, but also, under normal circumstances you will never run out of it. Be aware, however, that contaminants like moisture, dirt or air in the system can degrade its overall operation.
As a side note: The lack of a shelf life for refrigerant contributes to its appeal for competitive buying. There are some who purchase refrigerant which is about to be phased out, or for which pricing is anticipated to increase. They are able to hold the refrigerant for months or even years to maximize profit.