E-cigarettes generate high levels of aldehydes only in “dry puff” conditions (irrespective of the power levels)


By Dr Farsalinos

A new study by our team was published today in the journal Addiction. The study evaluated formaldehyde, acetaldehyde, acetone and acrolein emissions to the e-cigarette aerosol (vapour), distinguishing the generated conditions between normal and dry puffs.

This study is a result of severe personal frustration seeing the complete lack of understanding by several scientists on how e-cigarettes work and how they are used by consumers. You have certainly seen reports, accompanied by huge media campaigns, stating that e-cigarettes generate many times higher levels of carcinogenic aldehydes compared to tobacco cigarettes. We have always responded that such findings were the result of severe overheating of the device, which the vapers identify and avoid. We have repeatedly referred to the dry puff phenomenon as an explanation of these findings and why they were unrelated to realistic use. The authors of those studies and reports should have known the existence of the dry puff phenomenon since I have presented it in detail in a publication back in 2013! However, it is hard to explain this to someone who has limited background on e-cigarette function. So, it was time to present true evidence which, as always, have the strongest impact.

In this study we used 2 identical Kayfun Lite rebuildable atomizers. We deliberately prepared one with a double-wick setup, which would result in more efficiency and ability to withstand high power levels without generating dry puff conditions. The other one was a single-wick setup (silica in both cases) which was expected to be less efficient than the other one. Initially, we asked vapers to use both atomizers at different power levels for 4-second puffs, and we asked them to report when they detected the generation of dry puffs. The seven vapers unanimously reported the generation of dry puffs with the less efficient atomizer at 9 and 10W, while no dry puffs at those power levels were reported with the double-wick atomizer. Then, we replicated the exact conditions (4-second puffs, 30-second interpuff interval) in a smoking machine, using a power output of 6.5W, 7.5W, 9W and 10W.

The results were revealing. Minimal levels of aldehydes were detected at 6.5W and 7.5W with both atomizers. At 9W and 10W, the double-wick atomizer (which could be normally vaped at those power levels) again emitted minimal levels of aldehydes to the vapor.Those levels were 30-250 times LOWER than tobacco cigarette smoke. On the contrary, the single-wick atomizer (which generated dry puffs at those conditions) emitted large levels of aldehydes to the vapor at 9W and 10W, at some points higher than in cigarette smoke.

The results clearly show that of course you can generate as many aldehydes as you want from an e-cigarette. But you have to abuse it, to overheat the liquid at levels which no vaper could withstand. Power levels are NOT associated with high aldehyde emissions as long as vapers use them in normal and not in dry puff conditions. Obviously, none wants to vape at dry puff conditions…

The paper will be available online with free access to the full text for 1 month. I suggest everyone to read it, not only vapers but also scientists who want to be involved in e-cigarette research. It explains in great detail the dry puff phenomenon, Ohm’s law (eventually everyone will understand that power levels – Watt – and puff duration need to be reported, not voltage) and how vapers are using e-cigarettes. After this paper, there will be no excuse for anyone to report findings which are not relevant to realistic use and which could be misinterpreted.

The results are reassuring but, of course, the research on this issue is not over yet. We have tested only one atomizer. We need to test more, and we need to understand the consistency in dry puff detection among a larger group of vapers, as well as the effects of subohm, direct inhalation patterns. We tried to evaluate such patterns and the resulting aldehyde emissions few weeks ago, but to no success. We will intensify our efforts and will re-evaluate our methodologies and experimental setup in order to be able to examine this aspect too.

In any case, I and my team are glad and proud that we were able to provide valuable and high-quality information for vapers, smokers, regulators and the public health community. We would like to thank Addiction for the vigorous and constructive peer-review process which resulted in a high quality paper meeting the high standards of the journal.


The journal Addiction has released a press statement about our study, which can be seen below:


New study challenges claims on aldehyde content

of third generation e-cigarettes

In January 2015 a report published as a research letter to the New England Journal of Medicine (NEJM) (1) found that a 3rd generation e-cigarette (an e-cigarette with variable power settings) set to the maximum power and long puff duration generated levels of formaldehyde that, if inhaled in this way throughout the day, would several times exceed formaldehyde levels that smokers get from cigarettes.  Media worldwide accordingly reported this new health hazard of e-cigarettes.

A new study published online today in the scientific journal Addiction took a closer look at the NEJM findings in the context of real-world conditions.  It concluded that 3rd generation e-cigarettes can indeed produce high levels of aldehydes – but only under extreme conditions which human smokers can be expected to avoid because of the immediate unpleasant sensory effects.

The Addiction study, led by cardiologist Dr. Konstantinos Farsalinos, found that it was possible to get e-cigarettes to produce high levels of aldehydes, but only in what is known colloquially as ‘dry puff’ conditions.  As Farsalinos explains: “Our results verify previous observations that it is possible for e-cigarettes to generate high levels of aldehydes; however, this is observed only under dry puff conditions, which deliver a strong unpleasant taste that vapers detect and avoid, by reducing power levels and puff duration or by increasing inter-puff interval. Minimal amounts of aldehydes are released in normal vaping conditions, even if high power levels are used. In those normal-use conditions, aldehyde emissions are far lower than in tobacco cigarette smoke.”

To inhale more formaldehyde than that produced by a standard cigarette, a vaper would need deliberately and repeatedly to experience what one vaping blog (2) describes as ‘the dreaded dry puff’:  “Dry puffs, also known as ‘dry hits’, suck. They taste awful, can make you cough, and can also have the terrible side effect of leaving e-liquid in your mouth. Once you experience it, you’ll probably do all you can to prevent it from happening again!

Professor Peter Hajek, director of the Tobacco Dependence Research Unit at Barts and The London School of Medicine and Dentistry, UK, says of the Addiction study: “These findings emphasise the importance of making clear the conditions in which tests of this kind are undertaken and avoiding sweeping assertions that can mislead the public. Vapers are not exposed to dangerous levels of aldehydes. My reading of the evidence is that e-cigarettes are at least 95% safer than smoking. Smokers should be encouraged to switch to vaping.

-- Ends –


For editors:

Farsalinos K, Voudris V, and Poulas K. (2015) E-cigarettes generate high levels of aldehydes.  Addiction 110: doi:10.1111/add.12942

This paper is free to download for one month after publication from the Wiley Online Library: 

http://onlinelibrary.wiley.com/journal/10.1111/%28ISSN%291360-0443/earlyview or by contacting Jean O’Reilly, Editorial Manager, Addiction, This email address is being protected from spambots. You need JavaScript enabled to view it., tel +44 (0)20 7848 0853.


(1) Jensen RP, Luo W, Pankow JF, Strongin RM, Peyton DH. Hidden formaldehyde in e-cigarette aerosols. NEJM [Internet].2015 [cited 30 April 2015].372:392-394. doi: 10.1056/NEJMc1413069.

(2) The dreaded dry puff. 20 Feb 2015 [cited 30 April 2015]. In Vaporfi [Internet]. Florida, USA: VaporFi. 2015. [27 lines]. Available from: http://blog.vaporfi.com/the-dreaded-dry-puff/


Addiction (www.addictionjournal.org) is a monthly international scientific journal publishing peer-reviewed research reports on alcohol, illicit drugs, tobacco, and gambling as well as editorials and other debate pieces. Owned by the Society for the Study of Addiction, it has been in continuous publication since 1884. Addiction is the number one journal in the 2013 ISI Journal Citation Reports Ranking in the Substance Abuse Category (Social Science Edition).



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