Hello, My Name Is…

Every so often, something so bizarre pops up that I end up just taking a few minutes to absorb just how utterly bonkers it is before either bursting out laughing or face-planting my desk.

In this instance, I didn’t do either. First, a little history. Most of you know Clive Bates. Once a week, he runs a search on PubMed on everything THR related. It’s then bundled up in a nifty e-mail that he sends to a nicotine consumer group which I’m in.

Most of the entries have his comments, usually coupled with an excerpt from either the abstract of a paper or the conclusion. This one caught my eye out of the 32 results in Clive’s e-mail. (Clive’s comments in red)

Hi, we’re from a French lab, and you’ll like totally love our cool vaping machine, the U-SAV.

The U-SAV is recognised by the French association for standardization (AFNOR), European Committee for Standardization (CEN) and International Standards Organisation (ISO) as a vaping machine. It can be used to highlight the influence of the e-liquid composition, user behaviour and nature of the device, on the e-liquid consumption and aerosol composition.

One of the advantages of standards is the development of standard testing equipment and methods.

So, some researchers have designed a vaping machine. I had to check it out. Perhaps they’ve learned something.

Ladies and Gentleman, let me introduce you to the U-SAV:


This is their starting premise:

Globally, the design remains the same for all ECs: an atomiser connected to a battery, with the possibility to vary voltage, and power to control temperature. An EC is made up of a tank containing the e-liquid and an atomizer head (a metal coil wrapped around a wick usually composed of cotton). Depending on the models, the users can have a disposable cartridge (combining liquid and atomizer head), a cartomizer to be refilled (atomizer head already included) or a rebuildable one, allowing users to build their own atomizer head (choice of wick and resistor: metal, value, geometry).

For the most part, the fundamental design of an electronic cigarette is the same regardless of whether you have an Aspire Cleito or a ProTank. However, most devices now are variable wattage; mostly because it allows regulated devices to meet the wattage requirement without unduly draining the cells, unlike variable voltage. A cell can only provide a finite amount of juice before it simply can’t do its job anymore.

As with the “Juice Monster” paper, the researchers miss a crucial point. Passing voltage through a resistant material will always generate heat. That’s how light bulbs and e-cigarettes work. Most devices that have the supposed ability to moderate temperature, don’t actually sense the actual temperature of the coil. Instead, they take known variables (resistance) and the temperature coefficient (what resistance the wire is at certain temperatures) and program the device to back off on the power when it gets to a certain (user-set) level.

This temperature elevation heats the wick and evaporates the e-liquid. This implies the local drying up of the wick (where it is surrounded by the resistor) and the displacement of e-liquid by capillarity. Airflow through the atomizer is induced by the user’s inhalation, and this contributes to the thermal balance of the wire.

Maybe they have been listening.

The operator can choose between three different flow profiles (square, tooth saw, sinusoidal) and different modes:

  • Voltage: a constant voltage is applied during the whole manipulation,
  • Power: the resistor value is calculated every 150 ms by measuring current and voltage and the power supplied is regulated according to the evolutions of resistor value.

Or maybe they haven’t. Look. Under no circumstances, outside of a simulation, can a cell, or even a set of cells, provide a constant voltage. It is simply not possible. To truly simulate how a 18650 cell operates, perhaps the authors should take a look at the (widely available) discharge charts for commonly used cells.

In this study, the AFNOR protocol for the generation of emission is used. The manipulation is composed of 100 puffs divided into 5 series of 20 puffs. Each puffing cycle lasts 30 s, which include 3 s of aerosolisation and 27 s of rest. The inter-series duration is 300 s. The flow rate is programmed at 1.11 L/min (18.3 mL/s). The inclination of the atomisers is set at 45° during a series of 20 puffs and back to 0°, within 10 s, during the inter-series interval.

Seems fairly reasonable for once. Puff for 3 seconds (which is about average for most users), then rest for 27. Rinse and repeat. But hang on:

The manipulation is composed of 100 puffs divided into 5 series of 20 puffs.

Unless you are a chain vaper – and I know one or two – this simply isn’t realistic. After a few puffs, the coil will start to produce dry puffs because it is getting too hot.

Guess what happens when a coil heats up? Its resistance changes. Naturally, that doesn’t apply as much to a material used for temperature limiting such as SS316 or Ni200.



Figure 4a & 4b


As you’ll notice in the above chart, the resistance of the coil (a 1 Ohm Cubis head, SS316) signifanctly changes throughout the course of a single puff. In comparison, the amount of power (in watts) remains relatively stable; due of course to the regulation of power. I would, of course, be hesitant to vape on a 1 Ohm SS316 coil at 16W for a couple of reasons:

  1. A 1-ohm coil is usually used for mouth to lung vaping, and usually doesn’t require a large amount of power for the users satisfaction
  2. Applying a higher power to a coil that doesn’t have sufficient air-flow will result (eventually) in a dry puff scenario

Yet, look at this:



Figure 5 a, b & c


When set to variable voltage (which as we know isn’t at all possible), there’s variation in the power delivered (natch). It is, however, consistent (when set at 3.87V) with the variable wattage test. Suggesting that their crazy idea may actually have some merit.

We have observed the resistor value of the atomizer varies during a puff (Figure 4b). The transient slope observed during the first 250 ms is due to a fast temperature elevation that increases the resistor value. The plateau reached after 500 ms is the consequence of a thermal balance between the energy delivered by the battery and the energy collected by the surrounding environment.

Well, no shit Sherlock! Energy cannot be destroyed, but it can be transformed. Step to the front of the class. This is where a number of e-cigarette studies fail so dramatically.  It is also something decidedly lacking from a standard smoking machine.

Put it this way, very few vapers use their device in the same way they smoked. When smoking, the actual puff isn’t that intense. So all the previous studies that used smoking machines wouldn’t even come close to using the devices the way they are intended to be used.

We present in this study a novel vaping machine, U-SAV, which has the ability to generate, control and measure the electrical energy supplied to the resistor.

Well, congratulations. You’ve finally caught on to how vapers use their devices. It’s only taken you a decade.

Because of its characteristics, U-SAV appears to be a suitable machine for standardized regulatory assessment of EC devices, Tobacco Products Directive (TPD) compliance and for research purposes. It can be used to study the influence of the main physical parameters of EC function such as power, resistor, puff number and duration, and how these parameters affect emissions.

For once, I actually agree with a conclusion. But there’s a problem, and it has nothing to do with the paper itself.

The researchers have been led by the Laboratoire Français du E-Liquide (LFEL) research and development team. The LFEL is an actor and a committed defender of the independent vape.

This statement of COI is enough for many anti-ecig folk to completely ignore the contents of the paper and instead cry “Big Tobacco shills!”.

I wonder how long it will be before this paper is decried as an industry plot?

(image credit Marc Bruxelle/shutterstock.com)

3 thoughts on “Hello, My Name Is…

  1. Some thoughts on the “constant voltage”.

    I think they didn’t mean the actual battery cell but the whole VV power supply including control cirquits. Most advanced devices can compensate the inevitable volt drop at the cell by boosting. That’s actually the same basic mechanism that VW devices use. The only difference is that VV devices only measure the output voltage, while VW also measures the current to calculate the effective resistance and power.

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