Do you think it's the vaporizer or the stimulant effects of cannabis at work that would cause tightness in your chest? I do not own a Volcano, though I have smoked from a vaporizer before and experienced some vigorous tussi after a lengthy rip. I'm pretty sure cannabis has the capacity to increase both blood pressure and heart rate which could explain your situation. I'd say...just reduce the dosage a little bit and see what happens.