Here is a Feb 2012 update to reflect current events, and to ensure that people understand the current ECF view.

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Below, some incidents are described that involve XL specials, called 'mods', with two lithium batteries inserted in series to provide high voltage. These large metal tube mods with stacked batteries are the ONLY type of device implicated in recent incidents, and cautions mainly apply to these mods. Other types of e-cigarette ARE NOT affected.

Single-battery mods are not affected.
Regular e-cigarettes (minis and mid-size models) are not affected.

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In early 2012 there have been two recent events, one with no subsequent news but with separate reports of veracity from three members; and one in FL widely reported in the world media, which has done us no good at all. The two most recent events appear to have been serious, with the victims in ER after suffering extensive facial injuries.

This unfortunately shows that the situation is not improving, probably simply because the number of mods being sold is increasing dramatically.

Here are some itemised points of note:
  • ECF has had a total of around 8 reports of 'facial explosions' and 'rocket-mode fails' now. However, asking around vendors, many of them do know of events that were not reported on ECF and where teeth were knocked out or similar. This leads us to think there may have been about double this number - perhaps 15 blowups in total.
  • All explosions reported so far involve metal tube mods with two batteries in series.
  • Box mods are not implicated. Apart from electrical factors such as a plastic or wood body, there is the likelihood that gas will escape from a squonk hole, and/or the lid/door will simply blow off at the first outgas stage before the violent second-stage outgas.
  • Single-battery mods are not implicated, as far as we are aware at ECF.
  • Regular e-cigarettes are not implicated, as far as we are aware at ECF (minis like the 510 and KR808).
  • The explosions started a long time ago with early 2-cell mods, and still occur with the latest 2-cell models.
  • All lithium battery types, either single or in pairs, can suffer from a meltdown including heat, gas and flame. There are no exceptions to this. There is no such thing as a 'safe' lithium battery of any kind. There is a difference between meltdown and explosion though: the explosions causing injury always happen to stacked batteries in metal tube mods.
  • The safest battery is the largest battery, because one of the factors that causes the explosions is that the batteries are too small for the job. Smaller batteries ARE NOT safer. Even a little RC123 cell (16340) has around the same explosive power as a grenade of the same size. It's more than enough to do the job, when it's in front of your face.
  • All reported explosions have involved paired RC123-size cells: that is, 16340 size batteries used in series, aka 'stacked'.
  • Any/every size and type of cell can be reported as involved in a meltdown, since every cell will suffer meltdown if abused and/or faulty.

Some notes on mod safety features

Anyone who has worked in engineering for a few years will know the most basic rule of engineering, sometimes called Murphy's Law of Engineering: if it can go wrong, it will someday, at the worst possible time.

To build a mod without taking this into account (and especially a metal tube mod) is not something done by an engineer, it is a lash-up done to save $5. Don't buy a metal tube mod that can use two batteries if it has no safety features: it wasn't built by a competent engineer.

Murphy's Law means that a safety cutout will fail. It means that two separate safety features will fail at the same time. And finally, it means that to protect the user, ideally, some way of preventing injury needs to be incorporated that cannot go wrong because it is a physical feature.
Example: a mod with a large hole in it somewhere cannot explode - because it isn't sealed. This sort of measure is needed to defeat Murphy's Law.


Gas vents
In all the reports of explosions we have received where there was some way gas could escape, there was a first-stage outgas lasting about two seconds where hot gas and flame vented strongly from available apertures, followed by a violent second-stage outgas where, if there was not enough vent cross-sectional area to release the gas, the mod exploded. Gas vent holes will not stop such an explosion.

In other cases, there was sufficient vent cross-section, and the second-stage vent resulted in a violent outgas but no explosion. In this case, fires were started when the mod was in contact with furniture or a carpet, as the mod acted as a small flame-thrower. Also, these cases have included incidents where the second-stage outgas was of such force that the mod launched itself like a rocket.

What this shows is that small gas vents are simply a warning device. If they are placed for example around the circumference of the mod tube - the ideal position - then the hot gas and flame of the first-stage outgas will burn the holding hand and the mod will be dropped. The explosion then occurs when the mod is on the floor, away from the face.

With no gas vents at all, if the batteries go into thermal runaway, there is no warning and the mod explodes in the face.

The ideal design for a metal tube mod would be to have three milled slots in the tube body: three slots, equally spaced around the circumference, of around 50mm x 4mm, 2 inches x 5/32nds width. This cross-sectional area should allow the second-stage outgas to escape without causing an explosion, and a blowout plug would not be needed.

Mini e-cigs
Minis like the 510 and KR808 don't explode, even though they are steel tubes. This is because they all have built-in digital monitoring and protection, and a bottom-end blowout plug. Meltdowns do occur but are not common.

Mid-size e-cigs like the eGo and Riva are not likely to explode in use because they have integral protection. If they all had end plugs it would also help - those with a bottom-end USB charge facility in effect have a blowout plug. Others have a sealed lower end. As single-cell units, the risk is low.

However they seem to suffer from more meltdowns than any other type, perhaps because the load on them is generally higher (when using LR fittings for example) than on the minis, and the management circuitry being similar. The tiny circuits may have to take 2.5 amps DC, and this is a lot for micro-electronics in a very small package. They also fail when on charge (this seems the most common fail mode and is not under discussion here, it does not threaten the user's safety - it is a charger / device quality issue). Owners should also not leave them on charge as the cheap charging devices used are hardly all likely to have adequate protections.


Mod / battery failure modes

There are three failure modes we know of:

1. Meltdown mode
A battery fails and melts down with extreme heat, flame, and some gas. This can occur to all and every lithium battery type when provoked. There is no type of lithium cell immune to this, all have been reported as failing in this mode. It is simply to be expected, when abused.

Abuse = overcharged (on a faulty charger; or simply left on a cheap charger), or asked to deliver too much current for the cell size, or dropped and damaged, or showing a clear electrical issue but never checked on a meter, or the outer sleeve torn and the cell shorting out to the metal body of the mod, or the on/off switch jammed on in a pocket, or something shorted out by keys or change in a purse, or a faulty adaptor shorting out - etc. There are a lot of ways to make a battery fail.

2. Rocket mode
This is where the second-stage outgas, which is violent and prolonged, manages to find sufficient vent cross-sectional area to avoid a containment explosion, but the powerful gas jet exiting the large hole propels the mod away like a rocket, complete with flames, in a spectacular firework effect. The gas from all lithium battery failures is hydrogen, which is produced in large volume when some cell types fail, and ignites when there is a heat source of sufficient temperature, which the cell failure will eventually provide.

3. Grenade mode
With no real gas exit of any significant cross-sectional area, the mod explodes at the second-stage outgas. If there were no weak point at all, the casing would fragment like a grenade, since what we have here is basically a pipe bomb: a sealed metal container with an internal fast gas production source. However there will always be one weak point: the atomizer connection. If nothing else blows, the top end fitting (carto or atty) will be blown off into the user's face.

With a bottom-end blowout plug, this will blow off first. The reaction vector will propel the mod into the user's face with a very fast, short, sharp shock - but no serious damage will be done. There might be damage to the holding hand, if the end was obscured by the hand at the time.

All these fail modes have been experienced, and reported on ECF.


Time factors
Explosions seem to happen immediately after charging, on first use, on the first press of the switch. Every report with full details says this.

With an available gas vent or vents to show it, there is usually a first outgas of about two or three seconds, producing an intense jet of hot gas from the vent/s.

An explosion may then occur (frequently after the user has dropped the unit); or if there is sufficient gas vent area, the outgassing sharply intensifies and a jet of gas strong enough to act as a flamethrower may be produced. It seems a good idea to have dropped the mod by this stage. With no large gas vents, the unit would simply explode. Two or three small gas vents do not qualify as 'large' vents here, they just do not have enough cross-section to vent the huge volume of gas produced very rapidly. It needs large slots or a hole of maybe 16mm / 5/8ths inch.



Current advice
So that is the basic information we have at this date. As a result, the following advice can be given at this time:
  • For ultimate safety, use a single-battery mod.
  • For high-voltage, use a single-battery mod with a booster circuit of some kind.
  • Use the best and most expensive battery you can get. It doesn't seem worth it to economise on batteries. Our opinion is that, at this time, the AW IMR 'red' cell has the best reputation. It is a lithium-managanese 'safe chemistry' cell that does not need the integral protection circuit a Li-ion cell needs. Although these have never been known to explode, no lithium battery, ultimately, is absolutely safe: they will certainly meltdown with plenty of heat and flame if abused; and if they were sealed into a perfectly gastight container, and then made to fail, an explosion might result under those particular conditions.
  • We know that using a two-battery metal tube mod is intrinsically more dangerous because these are where the explosions are.
  • Using such a mod with no proper gas vents and no bottom-end blowout plug seems to involve the highest risk.
  • You should think very carefully before buying a metal tube mod with no physical safety features.
  • Mods need safety features because nobody really knows what battery they have, you just assume it is what it says on the label. But there are a whole lot more Gucci handbags out there than the factory ever made. Lots of people think they have a Gucci handbag but they don't. So, you may think you have two AW cells, but they could be cheap clones with counterfeit labels. And they might not even be Li-Mn cells: they might just be unprotected Li-ion cells.
  • Mods need safety features because users make mistakes. Everybody makes mistakes. If your safety depends on never making a mistake, then you are not safe.
  • Mods need safety features because the battery condition may be faulty but not have been noticed. Some mod owners don't even own a meter, so we know this is going to happen in some cases.
  • Mods need physical safety features because electronic ones might fail. That's what electronics does. And according to the most basic law of engineering, it will fail at the worst time in the worst way and in a chain of failures. People who say it can't happen aren't engineers and should not be building consumer products to be used in front of the face.
  • You should think very carefully before buying the cheapest batteries you can get, then stacking them. Especially in a metal tube mod. And especially in one short on safety features.
  • Batteries all have a C Rating. Don't use batteries with a C Rating below 2 amps (2,000mA) as they ARE NOT up to the job.
  • Bigger batteries are safer because they can handle the heavy load an atomizer puts on them. No big battery (i.e. an 18500 or larger) has ever exploded.
  • All batteries can meltdown and cause a fire if faulty and/or abused.
  • DON'T put a mod in your pocket or purse with the atomizer connected or the master switch (if fitted) on; or along with keys and change.
  • Adapters can be treacherous, so be careful - they can short out.

Economies
In the final analysis, mod explosions are caused by corner-cutting and economies of one kind or another.
  • If the mod has a chain of safety features, including the most important of all: a big hole somewhere - then it can't explode.
  • If you buy the best batteries you can, and actually receive the genuine article (which you can't guarantee unless you strip them down), and if they are checked regularly, then it is unlikely they will fail.
  • If you buy $3 batteries then accept the fact they are less safe than $10 batteries.
  • If you buy the cheapest battery charger you can, again, you are adding to the risk.
  • Every decision you make, where you cut corners, doubles the risk (or whatever).
  • When the mod maker cuts corners, and you then make more economies, the risk is mounting.
Start with a mod that has electrical and physical safety features; buy a good battery charger; buy the best batteries you can; and check everything regularly. To minimise risk (most likely to a near zero-risk situation) you would buy a single-battery mod, the best charger you could find, use only AW batteries or similar, and check everything daily. It's your choice if you don't do that; and you need to be very careful if you go the two-battery route. How much is your eyesight worth?

There is a very powerful trend among mod makers to develop new features, new shiny widgets, and new stylish looks. There is no trend, unfortunately, to develop new safety features - and in the end it is only pressure from ECF that forces them, eventually, to incorporate vital safety features.

There is something fundamentally wrong with their design process - which YOU will pay for unless you personally ARE VERY CAREFUL.


At ECF we are coming to the conclusion that all metal tube mods that are designed to accept two batteries, or that could accept two batteries, should have three milled gas vent slots along the body. This is the only single safety feature that will probably always prevent an explosion when other factors combine to create one.