After an eventful day where debate and panic settled in the community with the "dry-burn affair", Dr Konstantinos Farsalinos wished to react via his site " E-cigarette-research“, Here is his answer:
« By Dr. Farsalinos and Pedro Carvalho (expert in materials science)
There has been a lot of talk about my statement in the interview Friday May 22 on RY4 radio regarding Dry-burn. It is a process in which vapers prepare their coils by applying a lot of power to the coil without wick or e-liquid heating it to a glowing red. The main objectives of this operation are to:
a) Check the homogeneous distribution of the temperature over the entire length of the resistance.
b) Avoid hot spots.
c) Clean the metal of residues due to manufacture or because of the previous use.
During my interview, I mentioned that heating a resistor blank was not a good idea on the first try. Since then, I have received a lot of responses, emails and requests from vapers to clarify this point, provide evidence and explain the questions related to this process. I also received data sheets and specifications of the metals used for the resistors, and showing that they are stable at extreme temperatures (usually 1000 ° C or more).
First of all, I have to say that the reactions from the vape community are a bit exaggerated. I never said that using dry-burn made vaping more harmful than smoking. Obviously, some vapers who are used to practicing it for a long time obviously did not appreciate my statement. But please remember that my role is not to say what everyone expects, but to say how things really are. To better explain my statement, I invited Pedro Carvalho, a materials science expert with good experience on the metal structure, its composition and its degradation. Pedro also has extensive knowledge on e-cigarettes and is relatively well known in the vaping industry in Portugal and abroad. This statement was prepared jointly by Pedro Carvalho and myself.
Vapers should realize that the metals used for the design of coils are not made to be in direct contact with liquid on a continuous basis, to evaporate liquid on their surfaces and to be inhaled directly by a person. We are in a completely different phenomenon from what the specifications of the metal may suggest. We now know that metals have been detected in the vapor created by the e-cigarette. Williams et al. found chromium and nickel which came from the resistance itself, and this even if the resistance did not undergo dry burn. Although we have explained in our analysis the risk assessment and the fact that the levels found were not a major health concern, this does not mean that we should accept unnecessary exposure even if small.
For a "Dry-Burn", the resistors heat up to temperatures well above 700 ° C (we measured two temperatures under these conditions). This should have important effects on the structure of the metal and the bonds between these atoms. This heat treatment in the presence of oxygen favors the oxidation of the resistance, changes the grain size of the metals or the alloy, helps to create new bonds between the metal atoms, etc ... To understand, we must also integrate the fact of the continuous contact of the resistance with a liquid. Liquids can have corrosive properties on metals, which can further affect their molecular structures and the integrity of the metal. Finally, the vapoteur inhales this vapor directly from the resistance itself. All of these factors can contribute to the presence of metals in the vapor. Most of the materials that are used in the e-cigarette are not intended for. In this specific case, the resistive wire is developed and used as a heating component resistant to high temperatures even though no vector can transport the oxidized particles of metal in the human body. This does not mean, however, that it can be used in the vape in the same way.
Several studies have shown that the oxidation of chromium can occur at a temperature equivalent to the process of a “Dry Burn” [a, b, c]. Although these studies show the formation of a less harmful chromium oxide, Cr2O3, we cannot rule out the formation of hexavalent chromium. Hexavalent chromium compounds are used in various ways in industry and are often used for their anti-corrosion properties in metallic coatings, protective paints, dyes and pigments. Hexavalent chromium can also be formed when performing 'hot work', such as welding stainless steel [d, e], melting metal and chromium, or heating refractory bricks in buildings. ovens. In this situation, the chromium is not original in the hexavalent form. Obviously, we do not anticipate such conditions and at the same level for e-cigarettes, but there is some evidence that the metal structure can change and that we could find metals in the vapor of e-cigarettes. Taking all of these facts into consideration, we believe this “dry-burn” procedure should be avoided if possible.
Is exposure to metals important for dry burn on resistance? Probably little. This is why we think vapers over-reacted to my statement on RY4radio. However, we do not see the point of being exposed to metals in a high way if something can be done to avoid it. There may be other ways to deal with resistance issues. We think it would be better to spend a little time building a new coil rather than cleaning it up by doing a “dry burn”. If you want to remove residue from the kanthal making process, you can use alcohols and water to clean the wire before preparing the coil. If you feel that the setup may have hot spots, you can always lower your power level a few watts, or spend more time preparing your resistance. Obviously, if you want to harness and use all the watts that a device can give you, then you might find it impossible to do so without "dry-burning" the resistor. But then, don't expect to be exposed to the same levels of harmful substances as vapers who don't. Another thing: if you want to consume 15 or 20ml per day while doing sub-ohm by direct inhalation, don't expect to be exposed to similar amounts of harmful chemicals as if you have conventional use (even by direct inhalation). ) by consuming 4 ml per day. This is just common sense. We need to and will do research to quantify exposure (which we don't think is very high), but until then let's use the precautionary principle and common sense.
We confirm our opinion and obviously think that doing "dry burn" on the resistors will not make vaping a similar or more dangerous act than smoking. Let this be clear, there is no need for more feedback. However, we should reach a point where e-cigarettes should not only be compared to smoking (which is a very bad comparator) but should be evaluated under absolute conditions. If anything can be avoided, vapers need to be aware so that they can just avoid it. »
Sources : E-cigarette research - Translation by Vapoteurs.net
