Oh, that statement was not in the context of relying on the temperature of the exiting vapor to determine the production of anything. It was in response to an issue raised about the exhaust temperature from the chamber was. from this quote "....what is the actual temperature of the liquid/vapor? I guarantee we aren't really inhaling 450 degree vapor."
We know they didn't test any e cig. We also know we don't vape the way that test was conducted. They stated that right up front in the study. What they did say was VG can break down to formaldehyde when heated to a temperature of 470F and higher (well a small bit below 470F but that seems to be the primary inflection point). There is nothing inaccurate in their finding that I could see that would make me doubt that result in the test setting applied.
The problem isn't that study. The problem is Evolv using that study to suggest by indirect means that the study supports the need for temp control or else. If Evolv used the chamber temperatures and reproduced the same release of aldehydes from actual tanks with actual coils powered by actual TC boards, there would some validity to their position. They did not do that. That test needs to be done. Anything else is pure speculation.
Dr. F's tweet is factually correct. It also stated by the authors this was not an e cig. However, that factual statement does not refute the results. The question remains does contemporary vape gear produce aldehydes at significant levels with higher temperature use that vapers might reach? If so, at what temps in vape gear, and are they the same as in this study? And if true, is temp control required to prevent that or are other strategies just as effective?
As flawed though they are by not ensuring dry hits are not encountered during e-cig testing, I put far more credence in studies on actual vaping devices than the study of VG in a heated tube test, which I totally discount as far as any direct relationship to vaping, and only of value to showing what temperatures VG and PG (NOT coils) start releasing significant amounts of aldehydes (which to me is still very valuable information, yet unfortunately information misconstrued throughout this thread as temperatures we must not let our COILS reach).
I've seen several studies showing generally much lower aldehydes in ecigs/vaping devices than in cigarettes (or the "tube test"). This study, though a bit dated, for example is decent in the fact that though it shows a very high amount of aldehydes in a CE4 obviously misused to the point it damaged the coil, did indeed point out that damage. And it also showed significantly lower aldehydes than cigarette smoke for a Nautilus and a Subtank, even at higher power levels:
Effect of variable power levels on the yield of total aerosol mass and formation of aldehydes in e-cigarette aerosols
Of particular interest is Section 4 Discussion, which states in part:
"As shown in
Table 4, formaldehyde yields for Device 1 exceeded both the yield from combustible cigarettes (20 per day) and the OSHA limit even at the lowest power level and, at the maximum power level, produced formaldehyde almost 10 times the OSHA workplace exposure limit. This device also exceeded the acrolein yield from 20 combustible cigarettes per day and the OSHA workplace exposure limit, but only at the highest power level tested. Device 2 also exceeded the formaldehyde yield from combustible cigarettes but again only at the highest power level tested. In contrast, the other three devices all produced aldehydes below both combustible cigarettes and the OSHA workplace exposure limit. One device, Device 5, produced less than 1% of the aldehydes delivered from 20 combustible cigarettes per day and the OSHA workplace exposure limit. Also, there was over a 750-fold difference in total aldehyde yield between Devices 1 and 5. The extreme levels of aldehydes produced by Device 1 indicate that the coil may have overheated due to lack of liquid in the wick. In this case, the excess energy would be transformed into heat and the coil temperature would exceed the evaporation point of the e-liquid (22), with heat-induced decomposition processes competing with aerosolization. At the conclusion of this study, the coil for Device 1 was examined and found to be charred, an indication of thermal decomposition. The charred coil, the observed decrease in yield in mg/watt production at the highest power level, and the elevated levels of aldehydes and acrolein, all indicate that the results for Device 1 may not represent typical usage of this device, we hypothesize, and a typical user might experience noxious dry-puff effects and discontinue use at that power setting. However, determination of dry-puffs is outside of the scope of this study since dry-puffs can only be confirmed by sensory evaluation of the aerosol by a user (
Farsalinos et al., 2015)."
I would love to see studies using TC control devices, verified by testing to be accurate at the temperature setting used in the test, vaping pure VG, pure PG, at 400 deg F, 450 deg F, 500 deg F, 550 deg F, using cotton wicks, and also verified by real vapers to not be providing dry hits at those temperatures. So lets see aldehyde levels at known COIL temperatures. My predictions using common sense knowledge of the cooling effects of vaporization, the fact that the PG or VG in the wick is NOT at the coil temperature except at the points of molecular contact, are that we will see far lower (but not insignificant at higher temperatures) aldehyde levels than that produced at the tube test temperatures. And the results will therefore mirror the more applicable testing done with actual vaping devices than the tube test, which after all, was not a vaping coil temperature results test, but a test of the aldehyde release of VG and PG temperature.
Oh, one closing note, who the heck ever took 5 second draws off of a CE4. No one ever I knew of
More than most realize, VG, mebe?
