There’s been a lot of talk recently about mechanical  -“mech” – mods and what part, if any, they have in the future of vaping. As usual it’s been sparked by a news story; this one was about a 30-year-old American vaper who lost seven teeth when his mech mod exploded in his face.

Electronic cigarettes have been under attack for years, but the details of that attack have changed over time as new evidence steadily shuts down anti-vaping arguments. Battery safety is one of the issues that’s attracting a lot of attention right now, and one of the main reasons for that is a trickle of accidents – not common, but sometimes spectacular – involving mech mods.

So what’s a mech mod?

Mechs were developed not long after vaping started to become popular. The earliest e-cigarettes had a few limitations and one of the biggest was lack of power. The batteries were tiny and the circuitry was crude, so while they were fine as a proof of concept they weren’t all that good at actually producing vapour. Mech mods were the answer.

Although they’re usually classed as e-cigarettes, mechanical mods aren’t actually electronic at all. There are no circuit boards or wiring; they’re purely electromechanical. The basic design is a battery compartment, usually a metal tube, with a connector for the atomiser at one end and a mechanical switch.

By using larger batteries and eliminating the circuitry mech mods delivered a lot more power than first-generation e-cigs, and that meant more vapour and better flavour. They were also simple – so simple that anyone with decent metalworking skills could make one themselves. That let people get involved in creating new designs, which played a big role in building the modding community.

It’s also possible to make a mech mod very small; there’s no need for a screen, circuit board or any other electronics – just the battery itself, the atomiser connector, and a simple push-button switch.

mech mod
A mech mod with a walnut dash. Stay classy.

Nothing is perfect

Of course, there are disadvantages too. There’s no way to adjust the power delivery, for example. You get what the battery gives you and that’s that. The power isn’t stable either. As batteries discharge their voltage falls. With a regulated mod you set the power you want, and the circuitry will deliver that until the charge gets too low and the device shuts down. With a mech the power falls away steadily as the charge is used up, and there’s a big difference between the vape from a freshly charged battery delivering 4.2 volts and an almost dead one putting out 3.2.

There’s one other disadvantage to mechs, sadly, and that’s that they’re a lot less safe than regulated devices. If used sensibly they rarely have problems, but the fact is their simple design makes it easy to get things wrong.

Although the media talk about e-cigarettes exploding, the real issue is the batteries. A charged lithium ion battery has a lot of energy packed inside, and if that energy escapes in an uncontrolled way – for example if it’s short-circuited – it can generate a huge amount of heat. That boils the battery’s electrolyte, it bursts open and the wreckage usually catches fire. If all this happens inside a mech mod one of two things will probably happen. An end cap will blow off, turning the mod into a rocket as hot gas is blasted out of one end, or the whole tube will burst. Either way it’s pretty dramatic.

Safety is complicated

A modern regulated mod’s circuitry has safety features. If you fit an atomiser that’s coiled at too low a resistance to run safely, or that has a short circuit, the mod will detect that and refuse to fire. With some older or cheaper mods it might fry the board and kill the mod, but it won’t short the battery and cause an explosion.

On a mech mod there’s no circuitry and no safety features. If you built the coil wrong, as soon as you press the fire button the battery will short. If the resistance is too low you’ll draw too much current and push the battery past its safety limits. Either way, it’s likely to overheat and burst – and the mod will let it happen.

18650 e-cigarette battery
An 18650 battery.

Hybrids, and why to avoid them

Finally, a word about hybrids. Most mech mods have a top cap that the atomiser screws into. In the connector is an insulator, with a metal pin in the centre. The threaded stud on the atomiser is the negative terminal, and this is in contact with the top cap; the positive terminal in the centre rests on the pin. When the switch is pressed that closes the circuit.

Hybrids are different. There’s no pin, just a threaded hole in the top of the mod. The atomiser screws into this and its positive terminal directly touches the end of the battery. That’s fine if the atomiser’s positive pin protrudes past the negative terminal – but on many atomisers it doesn’t. They’re designed to work on modern mods with a spring-loaded centre pin, and if you screw them to a hybrid the result will be catastrophic.

If you put a tank with a flush positive terminal on a hybrid, both terminals will be touching the battery. This means that, as soon as you press the switch, you create a hard short circuit and your battery will probably fail spectacularly.

Be regulated

The fact is, for most vapers there’s now no good reason to buy a mech mod. A modern regulated device will deliver more power, more consistently and a lot more safely. There’s definitely no good reason for anyone to buy a hybrid, because they’re inherently flawed. If you’re new to vaping, or you don’t have a very good understanding of circuits, Ohm’s Law and battery safety, steer well clear of any type of mech; they just add an element of risk that you really don’t need.