Burning Sub-Ohm

In paper bought to my attention via Frank Baeyens, it comes as no surprise that, once again, tobacco control ‘research’ hasn’t got the faintest idea.

The paper, paywalled of course, grandly claims that users of Sub-Ohm Devices (SODs) are daily exposed to similar amounts of carbon monoxide as cigarette smokers. Yes, you read that right.


Depending on use patterns and device operation, users of SOD devices may be exposed daily to similar levels of CO as are cigarette smokers.

El Hellani, A et al (2019) – Chemical Research in Toxicology

Y’see, they’ve tried this before with the infamous ‘Juice Monsters’ paper which, with the help of Clive Bates, I had a comment posted on PubMed (since removed), but the crux of the comment can be found here.

In the ‘Juice Monster’ paper, the researchers completely disregard what we vapers know in terms of how to actually use a sub-ohm device. That is, most sub-ohm devices require a lot of power. Particularly if the device is powering dual, quad, or octo coils.

In this new paper, the researchers demonstrate the same complete lack of understanding. You’d think I’d be unsurprised by this. In fact, the level of stupidity in this one is on a completely different level to the ‘Juice Monsters’ paper.

First off, the device they chose was this. A VGOD ProDrip. Powered by this, a Lavabox; likely to be the DNA200. Why? You’ll see in a minute.

As the mod is an RDA, the researchers took it upon themselves to build their own coils. Imagine the hilarity. Naturally, because it is ‘science’ *cough* they did in fact make coils from kanthal, nichrome, stainless steel and nickel. All the common materials used in coil construction.

Here’s where it gets somewhat interesting. The coil ‘build’ for each of the materials was 10 wraps with a 3mm inner diameter. As they used Steam Engine, as most vapers do, to construct the coils I had a look at the various recommendations for each coil type they built.

First up, Kanthal. With a gauge of 24AWG, inner coil diameter of 3mm and assuming single coil for 10 wraps gives a resistance of ~0.9 Ohm.

That’s not the best part.

According to Steam Engine, this type of coil should be used at around 41W. This is important, as you’ll see in a minute.

For nichrome, they don’t specify exactly which variant, so I have assumed N20. A 10 wrap coil using nichrome N20 gives a resistance of ~0.6 Ohm. Again, as with the kanthal the recommended power is 41W.

Stainless steel – again, no specifics mentioned in the paper so I’m assuming SS316 – gave a resistance of ~0.5 Ohm for a recommended 43W.

Finally, Ni200. A 13 wrap Ni200 (26AWG) coil would produce a resistance of ~0.09 Ohm with a recommendation of 31W.

Got that? All coils built, I say that while struggling to keep a straight face, for a ‘recommended’ power of 40-45W.

I haven’t reached the best bit yet.

Gas from a zero air tank was continuously fed into the small chamber built around the coil head to ensure an atmosphere free of CO2 and H2O.

Oh really? As this is ‘science’ this would need to be a constant variable to ensure consistency. A flow rate of 1 LPM was therefore chosen. Oh my days. This is problematic on its own. 1 LPM simply is not enough airflow for the chosen hardware. As I was reminded, a mouth-to-lung inhale is approximately 16.67 cc/sec ( = 1L/s), so for the VGOD RDA, 1 LPM is nowhere near enough airflow to prevent pyrolysis of the liquid or coil.

But wait, there’s more.

A vaping session constituted three puffs of a 3 s puff duration and 10 s inter-puff interval.

Someone, somewhere will be extracting splinters from their forehead after reading that.

The liquid in the ECIG was replenished after each puffing session to avoid any “dry puff” phenomenon.

They truly have no idea. Three puffs of three seconds each with a gap of ten seconds at high powers will burn liquid and cotton. So no, they didn’t avoid the dry puff phenomenon. In fact, they specifically created a regime to produce it.

The effect of power increase from 50 to 200 W (increments of 25 W) on the degradation of 30/70 PG/VG mixture was assessed.

Uh-huh. I’ll bet.

No PG/VG degradation products were detected when SOD was operated at P < 100 W

Well, of course not. Although I am a little surprised by that finding given the recommended power level of 40-43W. Not to mention, as Tom Pruen kindly reminded me, that one of the tests for ex-smokers is, dun dun dun! CO verification. I’m sure that slipped the minds of these researchers, natch.

The coil geometry defined by the number of wraps and the coil diameter also showed an effect on PG/VG degradation. Two dual coils of the same metal and diameter (3 mm each) wrapped in 5 and 10 folds resulted in coils with 225 and 417 mm2 total surface area (B versus A) and led to the formation of 2153.7 ± 1487.3 and 77.7 ± 145.4 mg/m3 of CO, respectively (Table 1).

At least they correctly identified coil surface area as a key component yet they are missing one, incredibly important, point. A vaper, using a device at 150-200W won’t be using just a single coil of 10 wraps. For power at that level, a vaper would likely use dual, triple or quad coils.

One point that I almost missed in the text was the testing of the ni200 coil and their specific comments on that testing.

The assessment of the effect of coil material showed that nickel was the most active in enhancing the degradation of the PG/VG mixture.

Well, what a surprised. Nickel coils are specifically used in temperature control. These fools no doubt ran the mod in power mode. Speaking as one who has, mistakenly, done the self same thing the result is not pleasant. It is, literally, an instant dry hit.

It’s information like that that is sorely missing from ‘research’ in this area. Which of course leads to conclusions such as:

This finding highlights the importance of regulating these devices, including the coil material and geometry

If these people actually bothered to involve experienced vapers – like Dr Farsalinos does – then the results would be completely different, which is, of course, exactly why they don’t.

In fact, the PG/VG degradation was initiated at higher powers in the case of a larger surface area (100 W for 10 wraps compared with 50 W for 5 wraps).

That’s not how coils work. But then, these researchers didn’t bother actually reading up on this, nor did they bother to reach out to actual users. But then, as I said, the results would have been completely different, which is, of course, exactly what they want.

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