The vaporisation of an e-liquid is governed by its chemical composition.Thus, it is possible to predict how a liquid will perform when vaporised for analysis of the emissions.

Electronic cigarette emissions are generated with vaping machines. Currently, atomisers on the market are used as reference devices and connected to these machines. According to laboratories, they can be different. An issue then appears: How to validate or invalidate emission generation if laboratories use different equipment? The solution developed and presented in a recent of ingésciences publication [1] is to characterise an atomiser with one or more liquids. Once calibrated, it is used in routine analyses. The strength of this innovative method was verified on 800 commercial liquids analysed.

20 e-liquidsto characterise a method

The atomiser qualified as reference by the laboratory is Cubis from Joytech. It is equipped with a resistance of 1Ω. The method of characterisation required 20 non-commercial e-liquids. The first 5 contain a mixture of propylene-glycol (PG) and vegetable glycerine (VG) at different volume ratios (PG/VG): 100/0, 80/20, 50/50, 20/80, 0/100. 5 others contain the same bases and are completed with 10% ethanol by volume. In 5 others 10% water is added. The last 5 liquids are enriched with 5% ethanol and 5% water. An e-liquid is considered to be mostly composed of these 4 compounds. The results show that the weight of e-liquid vaporised has a proportional relationship to the concentration of PG and VG. It increases linearly with the increase in concentration of PG. It decreases linearly with the concentration of VG. Adding ethanol amplifies this vaporised weight while water reduces it.

Reliable validation method

Then we can extract a calibration relationship from the measurements taken on the 20 previous liquids. This is conveyed by a relationship linking the amount of liquid vaporised and the density of the liquid. It can then be applied to commercial liquids. Just knowing the density of the liquid, we can then predict an amount of liquid vaporised after manipulation. The acceptable tolerance applied to the difference between the measurement and the prediction is 25%. This value complies with standard AFNOR XP-D90-300 part 3 on emissions. Since 2016, 800 commercial e-liquids have been analysed by the laboratory. 98% of the amounts of liquid vaporised after manipulation have less than 25% difference compared to the theoretical acceptance range calculated from the model. Still more interesting, 62% have less than 10% difference. This is what validates the method.

In each experiment, the U-SAV robot vaper was used. It is configured to follow the protocol of standard AFNOR XP-D90-300 part 3. The power used is 15W. This power appears as a reasonable use value of the Cubis.

[1] Soulet, S.; Duquesne, M.; Toutain, J.; Pairaud, C.; Lalo, H. Experimental Method of Emission Generation Calibration Based on Reference Liquids Characterization. Int. J. Environ. Res. Public Health 2019, 16, 2262.