How do exchanges work? Can I buy a tank private party and just bring it into a shop for an exchange? I’ve only bought CO2 and BrewChatter swapped those out no questions asked. I would think it’s the same for welding gases. I haven’t called any shops in town obviously because I don’t NEED a tank...yet. Just curious if I am given a tank that’s out of date if I should grab it as an exchange, or if shops must have ‘their’ tanks because ‘they’ certified them blah blah blah.