My tip for cannabis vapers: Pax 2/3 with a bubbler attached. You vape herb, not some chemical cocktail. Furthermore the bubbler filters out any tiny plant particulates as well as cools down the "steam". No combustion, no lung irritation. And the full flavour of the herb is yours to enjoy.

Really seems to me as the healthiest option, next to breathing (clean) air. (Although our air is far from clean. You might get clean air on a mountain top but at sea level you're all breathing exhaust fumes and farts )

As to nicotine vaping... I would stay away from that mess. Who knows what they put in that chinese e-juice.