No Refrigerant Left Behind
In the US at least, any refrigeration technician should already have passed his EPA 608 or 609 and be fully aware that venting a unit can cost him his card rendering him unable to buy refrigerants. Before working on all but small self contained units he must have access to a refrigerant recovery unit. This a compressor sort of thing that can move the gas from the installed unit into a tank for either reuse on site or taking to a reclamation center, where allegedly they can be paid for it.(Yes, my AC units broke and the time to even get a technician to look at them, was so long I researched how to diagnose them and do the easy fixes, ran into the EPA requirement, studied the material and got my EPA certification, bought a bunch of gear off Amazon and refrigerant from a “good old boy” at an exorbitant price (global shortage, plus most is sold in palette quantities), and fixed my own unit in half the time it would have taken to get an appointment with a professional company. The first unit is working. If I succeed at the second unit I’ll even be money ahead. Of course if my yak had already been shaved maybe it could have tolerated the heat.)