Vaporiser

In the context of medical cannabis, a vaporiser is a device that heats a measured quantity of Cannabis with hot air and collects the vapour given off, in a bag for inhalation by a patient.

Burning of medical cannabis creates toxins of combustion. Particulate toxins (tars) are reduced by the use of vaporizer. Medical marijuana and its use by the immunocompromised.
McPartland JM, Pruitt PL.
Altern Ther Health Med. 1997 May;3(3):39-45. Review.
PMID: 9141290.

Strictly in the context of medicinal cannabis use where legal, the only approved safe and effective Vaporization as a smokeless cannabis delivery system: a pilot study.
Abrams DI, Vizoso HP, Shade SB, Jay C, Kelly ME, Benowitz NL.
Clin Pharmacol Ther. 2007 Nov;82(5):572-8. Epub 2007 Apr 11.
PMID: 17429350 medical device is the Volcano® Vaporiser, by Storz & Bickel.

The Volcano® is certified in Canada and Israel as a medical device, and holds Medical Device Conformity MDD 93/42/EEC.

The Volcano® is the device used in the study, Low-dose vaporized cannabis significantly improves neuropathic pain. Low-dose vaporized cannabis significantly improves neuropathic pain.
Wilsey B, Marcotte T, Deutsch R, Gouaux B, Sakai S, Donaghe H.
J Pain. 2013 Feb;14(2):136-48. doi: 10.1016/j.jpain.2012.10.009. Epub 2012 Dec 11.
PMID: 23237736

It is always important to remember that ingesting anything into your lungs carries with it risks, as the paper from Rosa Ruchlemer, Michal Amit-Kohn, David Raveh & Lumír Hanuš, Inhaled medicinal cannabis and the immunocompromised patient, suggests. Inhaled medicinal cannabis and the immunocompromised patient.
Ruchlemer R, Amit-Kohn M, Raveh D, Hanuš L.
Support Care Cancer. 2015 Mar;23(3):819-22. doi: 10.1007/s00520-014-2429-3. Epub 2014 Sep 13.
PMID: 25216851 | Full article [PDF] from MASSC

Further reading

Wikipedia: Vaporizer
Health Canada: ASPERGILLUS SPP.