Under the SNAP rule, each alternative refrigerant must be used in accordance with the conditions listed below. If you choose to use an alternative refrigerant, make sure that you pay strict attention to these conditions. Each alternative refrigerant must be used with a unique set of service fittings to prevent the accidental mixing of different refrigerants. These fittings are attachment points on the car itself, on all recovery and recycling equipment, on can taps and other charging equipment, and on all refrigerant containers. If the vehicle is being retrofitted, any service fittings not converted to the new refrigerant must be permanently disabled .
Unique fittings help prevent cross contamination.
They also help protect the purity of the recycled supply of R-12, which means it will last longer, so fewer retrofits will be necessary nationwide.