You should not use R22 to do a sweep since this is highly polluting to the environment. You should if or if you use dry nitrogen. If you are on the subject of refrigeration, you have no choice but to buy a tube. With respect to CO2, if you use it for sweeping, then you would have to clean the circuit with nitrogen to remove traces of CO2 since it cannot be mixed with the refrigerants. Let's not forget how important it is to carry out conscientious work. Regards.