Re: Hate to be pragmatic but
As I said, a myriad of designs. But many therapeutic asthmatic "vaporisers" are actually atomisers. Atomisation can be achieved by physical methods which do not involve direct heat, such as nozzles or sonic bombardment. Stage smoke effects also come in a myriad of designs, from atomisation through dry ice to vaporised oil. I've said it before on here (and on other sites), and received massive criticism for it I might add, that the design of the heating element may well be critical in determining the purity of the vapour that is inhaled. A heating coil that is directly in the path of the inhaled vapour may well (actually it does and there are papers that back this up) contain nano-particles of metal which slough off the coil surface during the rapid expansion and contraction that heating causes. So any test on the oils and liquids which may involve vaporising them using, say, a heated glass flask, and then pulling the vapour into the atmosphere of a sealed rat or mouse cage, would miss out on that feature of the design. For comparison, it would be like saying cigarettes are safe if e.g. filter tips were made of asbestos but the experiment had been done using rolling tobacco. You've uncoupled the delivery system from the substance.
So what I'm saying it that extrapolating long-term effects from short-term studies or from laboratory studies which only test part of the whole is a bad thing to do. There are some subjects which just polarise people immediately - e-cigs, mobile phone radiation, Brexit; you're one side or the other and if you're one camp you have to smear the other at every possible opportunity, denounce their research, slander their supporters and attack, attack, attack. That's not how to do science.