So,
I AM somewhat of an environmentalist but I had a realization over the past few years:
ALL of the refrigerant that has ever been produced (or will be produced), whether it be R12, R134a, or any of the other (non-automotive) stuff WILL EVENTUALLY END UP IN THE ATMOSPHERE.
Think about it: Why do we have to repair and recharge systems? Because the refrigerant escaped...into the atmosphere.
I figure that prolonging this process (by recycling it instead of venting it) probably is beneficial (gives the atmosphere time to process it slowly, maybe...I don't know). But my main point is that it's kind of a "now or later" scenario. It's all going to get vented eventually...one way or the other.
Clem

