R22 is an old-style refrigerant gas previously used in air-conditioning systems and other cooling equipment. To combat the problem of the ever-increasing hole in the ozone layer, it was agreed under the terms of the Montreal Protocol
that ozone-depleting substances, including CFCs and HCFCs, would be phased out globally to help stem the problem.
It is now illegal to sell equipment containing R22 gas and many manufacturers are unable to provide even spare parts for these older systems. You are also unable to buy R22 gas in its original, untainted form although some alternatives are available; again, these alternatives are also being phased out. As a result of these changes, if you have an R22 system and it suffers a gas leak, it may not be possible to repair or refill your system.
If your unit is your sole source of heating or cooling and you have a failure, you may well be without heating or cooling for a considerable time. This could be potentially catastrophic if, for example, your system is being used to cool a server room. In the case of a major failure such as a burnt out compressor, then, in all likelihood, it would not even be possible to re-use the existing pipework because of contamination within the system, further delaying any repairs or replacement while increasing the costs of such a replacement.