The answer to this is that we don't know, as no specific research has been done into this - amazing as that may sound.
I, like many others of course, was interested in this question, so I looked at the available research. See this page on ECF for the result:
http://www.e-cigarette-forum.com/fo...9160-analysis-electronic-cigarette-vapor.html
The published resources are listed here and a brief resume of their content attempted. Essentially, no one has carried out a correctly-managed analysis of electronic cigarette vapor. There have been some studies, but:
- These were brief because another topic was being looked at as the main focus and the vapor content was simply a side issue
- Or, analysis was attempted, but the results were so poorly presented that the results are incomplete and therefore meaningless
- Or, photographs show the e-cigarette being used in a manner in which it cannot work correctly and therefore the results cannot be accurate
Taking a guess at some sort of answer, by combining various results in a way that may or may not be accurate, and which may only apply to one type or make of liquid refill, I came up with the following figures:
66% water
13% alcohol
3% PG
1.4% nicotine
...and around 17% not accounted for.
In order to do this I mainly used the most complete analysis, which nevertheless still showed one or more major faults. Obviously, 17% not accounted for is unacceptable.
The most anomalous figure though is the amount of alcohol. It is probably fair to say that another sample, and one obtained by operating the e-cigarette in a normal manner, would not show a similar amount.
Because of similarities between the various studies it seems likely (at this time and with the information we have at present) that around two-thirds of the vapor is water, and around 3% will be PG/VG. The remainder would appear to be mainly flavorings but there is no way to confirm that.
But a proper study needs to be done. As with all studies into electronic cigarettes, an experienced advisor needs to be present, otherwise many types of errors are likely to be made. The most obvious in these lab trials is that the e-cigarette was operated inverted in some (if not most) cases, and this means that results could not possibly have been optimal.
To answer your specific question, why does the vapor hang around, and at floor level? The answer is quite simple: it's very similar to disco fog. It will not disperse until the PG or VG that binds the water vapor particles has ceased to do so (perhaps by itself dispersing into a particulate size too small to affect water vapor, or by condensing onto surfaces such as the floor so that the water vapor becomes 'freed'. The PG and/or VG binds the water vapor and causes it to condense into larger particles than normal and thus become visible.
If the vapor collects at ground level, it is because it is cooler than the surrounding air. If you have seen TV shows where a performer stands in a cloud of mist around their ankles (the 'graveyard effect'), this is achieved by passing the fog
through a chiller before it is expelled onto the TV set, thus making it colder than the ambient air.
