ECF does not regard sub-ohm vaping as dangerous. This point needs to be made clear (or clearer), because we don't know of any serious risks with any sensible vaping practice. This advisory concerns the ways in which people can take what is normally safe and increase the risks, perhaps without knowing they are doing so. This especially applies to beginners and those giving advice to beginners. Sub-ohming has no known risks unless deliberate choices are made that will inevitably increase risk.


Sub-ohming is normally safe
Sub-ohm vaping has caused few serious incidents that we are aware of (just the one - see below), therefore we cannot describe this activity as risky when normal procedures are followed. There are dozens of posts on ECF that describe sub-ohming as 'dangerous', but there is little evidence for this unless a vaper goes beyond what is considered normal use.

However - any intrinsically safe activity can be carried out in a way that significantly elevates risk. It is especially important that beginners who have no history in vaping are not badly advised. There are certainly ways that an individual can make sub-ohming less safe than it should be, if they follow bad advice; therefore it is our duty to point this out.

This Advisory is entirely for the purpose of fully informing vapers of possible risks due to personal choices, and has no other purpose.


1. Batteries
Modern batteries are extremely safe compared to those we used to have. If a genuine IMR or hybrid rechargeable cell is destroyed by sub-ohming or some kind of fault, then what appears to happen is that it melts down without any significant out-gassing. The gas generation is the danger factor as it can lead to an explosion, if it takes place in a sealed device. A hot APV does not appear to be a significant danger except in some sort of fire-risk situation (maybe in a gas station, or on an old foam couch/sofa).

What is certainly an issue, though, is if a counterfeit battery is used by mistake; or if someone deliberately uses an ICR (regular Li-ion) cell instead of the modern type of safer-chemistry cell. In that case there could be a significant outgas risk in the event of a battery failure, which translates to risk for an explosive event.

- Please make sure to use genuine IMR or hybrid cells from a reputable source, and DO NOT USE regular Li-ion cells (ICR) for heavy-duty applications like this.
- The use of a sealed metal tube for a high-power application using lithium ion cells in front of the face is an intrinsically bad idea. Gas vents are a good idea, and the bigger the better - in case the wrong battery is used. This applies even more if batteries are stacked (placed in series) as the risk is multiplied up; until August 2014 the only explosive events known had all taken place in metal tube mechmods with stacked cells [1].
- At the August 2014 VapeBlast event (well named) there was an explosion that was probably a single-cell device although this is impossible to confirm as the equipment was completely reduced to shrapnel, so that is not possible to say if one or two cells were involved.


2. Ultra low resistance coils
August 2014: We have now had the first confirmed mechmod explosion due to sub-ohming, which took place at the recent VapeBlast event. The device exploded, blew a hole in the ceiling 20 feet above, brought down a ceiling tile, and burnt a hole in the floor. As this was witnessed by dozens of people (also, the explosion was heard by a hundred people or so) and the photos are widely available, it is impossible to deny that it occurred. It seems lucky that no one was hurt; indeed the mechmod owner ran away in order that if any injury occurred he wouldn't be held accountable and to avoid paying for the damage. As the device became hot he threw it down, then it exploded. The incident occurred at a Cloud Contest although it is not known if the vaper who caused the explosion was a bystander or a competitor; since he was clearly stressing-out his rig it seems possible he was about to compete.

What can be learned from this
An incident like this is caused by a chain of design errors, user actions, and possibly a battery fault.

- Sealed metal tubes will probably explode if a battery vents violently
- Small vents at the bottom of the tube are useless, only very large gas vents near the top have a good chance of preventing an explosion
- Building 0.2 ohm coils and under will raise the amp draw exponentially and this increases risk - the power graph takes a massive jump at 0.2 ohms and starts to climb vertically as resistance is reduced further
- Using cheap batteries with ultra low res coils is a certain route to high risk - it needs 30 amp batteries of guaranteed high quality
- Using a 26650 cell is intrinsically safer as it can take a higher load
- Using long draws or machine-gun draws to create monster clouds stresses the battery much more
- Cloud Contests are events where people put ultra high stress on their rig to create monster clouds; if spectating, you could consider standing at the back of the room to stay safe
- If you run a Cloud Contest then you should probably check that your personal and business insurance is really, really good and is appropriate for dangerous sports
- People are now discussing the safety (!) involved with putting 100-amp pulses on their batteries in order to create the biggest clouds with the lowest resistance coils; there is only one way this is going to go and you don't want to be within the explosion radius: someone may have a counterfeit battery, or one that is just too small for this extreme usage mode together with ignoring the device getting warm [2]



3. Inhalation issues

It is possible that the super-heating of e-liquids that takes place in an RBA run at less than 1 ohm may create some toxic materials. Tests have shown that these coils, in normal use, can reach more than three times the temperature of regular atomizers (which normally run at 60C to 70C) [3].

This is just plain logic and should not be seen as anything radically new: overheating refills creates some nasties and there is no way around that. It is possible that materials such as acrolein and aldehydes will be seen in measurable quantities, and some pyrolytic compounds may even be created.

Inhalation of sub-ohm vapor is probably not the same as regular vapor and therefore may have additional risk. It may create conditions where potential carcinogens (cancer-causing agents) will be seen in measurable amounts, and in that case there would be some elevation of risk, which will escalate as resistance goes down and heat goes up.

We can regard this as significantly more important than battery safety at this time: there is only one reported incident of an exploding mechmod in the modern single-cell era, and no reports of house fires caused by sub-ohm rigs self-destructing; but there are probably thousands of people inhaling materials that are simply not present in vapor from a regular clearo run at 2.5 ohms.

We don't know if there is significant additional risk, but it has always been ECF's duty to fully inform the community so that choices can be made.

Buttery flavors
We have to add a specific note on butter/creamy flavors here. Diacetyl or a similar substitute is present in some flavors, and it is likely that many of this flavor group have exactly the same issues as diacetyl, since they are all fairly similar molecules. Because of the sheer volume of liquid consumed and the volume of vapor created by sub-ohming, all issues related to refill liquid safety are magnified. Previously it was considered that consumption of 10ml of refill liquid per day was high; now there are rumors that some sub-ohmers may even consume 20ml a day and run 80 watts or more.

Until more information is available, our advice is that all butter/cream type flavors are avoided for sub-ohm use (inhalation of the butter-popcorn-custard flavoring diacetyl can cause the irreversible degenerative lung disease bronchiolitis obliterans, aka 'popcorn lung').

This warning is not pure speculation:
A research study has already indicated that the vapor created by high-power vaping contains more potentially toxic compounds
Dr Farsalinos' recent study reports that a very high percentage of cream-type flavors contain diacetyl even when the vendor claims there is none present
He states that 7 out of 10 vendors who claim there is no diacetyl in their products are not correct
It looks as if diacetyl is now being used widely as a flavor enhancer like MSG in food, as so many products contain it
What vendors say is clearly irrelevant - the only proof is a test certificate with a negative result
An additional issue is that most GC-MS systems cannot test down to a sufficiently low figure to detect the toxin, it requires a specialist HPLC-UV test according to experts



What ECF advises, at August 2014

If you don't want to take unnecessary risks:
It may be best not to go below 0.5 ohm coil resistance unless you are absolutely sure you know what you're doing
Pulling big amps by definition means a big battery is needed to stay completely safe - this means a 26650
If your mechmod starts to feel warm then you are going too far, and getting into the danger zone
If your battery self-destructs then nothing is going to save you except big gas vents near the top of the tube
Vaping 20ml of creamy sweet e-liquid a day could be putting your lungs at risk because of the fact that 7 out of 10 of these refills contain diacetyl even when ALL of the vendors selling them deny it - we don't know how this will play out because there is only about 1 year's experience of this kind of volume of consumption of known toxic materials
Vaping 20ml of superheated e-liquid a day out of a low sub-ohm RBA must have a higher risk than vaping 3ml of regular-temperature vapor out of a clearo; please recognize that all vaping doesn't have the same risk, and the choice is yours




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[1] Stacked cells

If you want to risk using stacked cells in a metal tube in front of your face (which is a really bad idea in the first place) then you must be absolutely sure they are not counterfeits and/or that you have very large gas vents. In the days before VV and RBAs, this was much more common - and there were some appalling facial injuries from explosions as a result. BE WARNED.

We very much hoped that we had seen the last of that practice as VV devices can generate any voltage and have electronic fusing, and RBAs allow a massive vape to be generated off a single high-quality battery by going low-res; but there have been some references lately to using stacked cells with an RBA. People can do what they like, but they should at least be aware that when this was done in the past, vapers ended up in the ER. Batteries are far safer now - but that assumes you have genuine batteries...

Our advice would be that if you truly need a monster vape and are using a low-res coil on an RBA, then use a single super high quality 26650 IMR or hybrid cell in a large-format mechmod. Anything is better than stacking batts and driving them hard in front of and partly inside your face in a sealed metal tube. We have seen the results of that and it was disastrous.

[2] Mechmods getting very warm
There are now instances where beginners are using towels to hold their devices as they get too warm for comfort. This is going into the danger zone no matter what type of battery is being used, hot materials could be expelled causing burns or setting fire to a carpet even if the battery does not explode. What will the next trend in vaping videos be - how to use welding gloves when vaping?

[3] Heat gun temperature checking
There are two ways to check a coil temperature: using a thermal imaging 'heat gun' checker, and thermal contact probes. We have seen tests by many people using heat guns that came in at 100C to 135C for sub-ohm coils, but have been told by a scientist working on these issues that contact probes give a different result that is significantly higher.

At this time, then, it appears that thermal imagers may not work as well as contact probes, and we prefer to take the professional advice that super-sub-ohm coil temperatures may be higher than is currently thought.