What fraction of the vapour in electronic cigarettes is water?

Question

Not a chemist but looking for an answer I can understand.

Electronic cigarettes use propylene glycol and/or vegetable glycerin as a base liquid. This is heated and vaporized at a low temperature (my e-cig is 7 watt). When exhaled the VG/PG absorbs water from the air producing the visible vapour cloud.

Assuming standard temperature ($\pu{20^\circ C}$) and humidity ($\pu{50\%}$), what ratio (or percentage) of the visible cloud is water?

It's not that I can't find an answer to this, just can't find an answer I believe. Most based on rumor and warm fuzzy feelings of what people want to believe.

Answer 1

The short answer to this is that there is no single answer to this problem as the vapor composition that is produced by any given atomizer is dependant upon a large number of components. To name a few:

• The initial composition of the liquid, which will vary flavor to flavor and manufacturer to manufacturer. You can find out a bit more about this with the following articles

  • Characterisation of mainstream and passive vapours emitted by selected electronic cigarettes DOI 10.1016/j.ijheh.2014.10.001

  • Electronic cigarettes: overview of chemical composition and exposure estimation PMCID: PMC4304610

      A note to consider with the above is that many toxic organic solvents such as Formaldehyde, Acetaldehyde, Acetone, Acrolein, Propanal, Ethylene glycol, and Diethylene glycol are found in eLiquids, in various concentrations.

• The temperature that the eLiquid is heated to internally (this affects the vapor pressures of the various components in the liquid)
• The concentrations of all of the, solvents, flavorings and such which are adsorbed by the person who is using the atomizer

Given all of these factors, and the large number that I am sure that I am missing, there is simply too many confounding variables to be able to give a straight answer to your question without directly measuring the concentration - not that I would know how you would make such a measurement.

Answer 2

Disclosure: I'm not a chemist.

First off you can't be sure what temperatures your atomizer reaches purely by wattage because it depends on coil resistance, material and if you run your vaporizer in TC mode (I assume you do not have that option available).

Humidity will only have a visual impact on cloud density after you exhale. Depending on atmospheric humidity glycerin molecules will effectively bond with water in the air. The more humidity it is, the more water will be picked up.

The ratio of glycerin to water in the cloud forming then will depend on: - temperature - humidity - volume of air in which the cloud is expanding

What I'm more interested in is if this contributes to atomizers popping (especially open air ones like RDA's). Say I leave it standing on my desk overnight soaked in juice. What will be the liquid water % be then.

Also how does this effect contribute to nicotine neutralisation? I red that it gets broken after contact with oxygen and I guess that it will get plenty of it while floating in an areosol particle.