Using Individual R-12 Cans
Disposable refrigerant cans (referred to as one pound cans) have a flat type seal or a screw type seal, and the proper can tap must be used for each type. Be sure sealing gasket on can tap is in good condition. A proper safety can tap will prevent refrigerant from flowing back into open can, as the tap has a one-way flow control.
NOTE:
Recent findings by the EPA indicate that R-11, R-12 and R-113 are harmful to the Earths' protective Ozone layer. Make every attempt possible, to avoid discharging R-11, R-12 or R-113 into the atmosphere.