I've also had a pneumothorax - only one, spontaneous, and in the right lung. I was treated with a chest tube and oxygen and it reinflated the next day. I haven't yet found a convincing answer as to whether or not its safe to vaporize after a collapsed lung. In the meantime I've been making the Green Dragon drink (see the thread in the Concentrates forum). That's worked pretty well, but I'd still like to vaporize since the Green Dragon takes about 2 hours to kick in and sometime lasts too long. I plan on making an appointment for a medical marijuana evaluation and I'll ask the doctor then.