There was a report from over two years ago of a Florida man who had batteries explode in his mod. Allegedly it was a home-made mechanical mod, and he was stacking batteries, and the wrong kind of batteries at that. Allegedly he was using non-rechargeable batteries like flashlights and boom boxes use. This was a particularly bad explosion which knocked out teeth and part of his jaw.
I myself have had an ICR protected Li-ion battery explode in a mechanical mod. The fire button got stuck on the mod, causing the battery to over-discharge and go into thermal runaway. Below is that battery:
Now, this was nowhere as near violent as what happened to that Florida man. But as you can see from the pic, the meltdown was enough to cause the battery to split open and vent pressurized hot gas hot enough to burn the pants pocket the mod was it. The "protected circuit" in the battery and the hot spring in the mod did not prevent this battery from meltdown.
Granted that was not one of the best batteries that I could have used, but it WAS the battery that was recommended for that mod at the time I purchased it, and I didn't know any better for the worse.
Protected ICR batteries use a flamable chemistry, so when the primitive circuit built into them fail, they can become quite dangerous. This is why these batteries are no longer recommended to be used in any mod.
The newer IMR and hybrid batteries use "safer chemistry" which do not require built-in protected circuits in them, as they are inherently safer. They can still vent gas should they go into thermal runaway, but they are less likely to and in less dramatic fashion than an ICR battery can.
The fact is a mechanical mod has little to no protection features like a regulated variable voltage mod has. A variable voltage mod will have short circuit protection, auto timed cutoff of the fire button, temperature monitoring, reverse battery protection, over-discharge protection, etc. built into the micro processor. Had I been using a regulated mod, the battery incident that I experienced would have been prevented from happening.
A mechanical mod's only "safety features" would be a collapsable hot spring (which some do not have), a vent hole to allow escape of the pressurized gas from a venting battery, and some have a lockable fire button to prevent accidental firing of the fire button. The first two only come into play AFTER a battery has become hot and is in trouble.
Therefore, a regulated mod is safer than a mechanical mod. Safe chemistry IMR batteries are safer to use than ICR batteries.
Having said that, I still use a mechanical mod. I use safe chemistry IMR type batteries in my mechanical mods and regulated mods. I practice safe battery habits. The chances that I will experience another battery incident is extremely small because I am using safer batteries, the right batteries, and practicing safe battery habits.
Learn which batteries are the safest to use in your mods. There's a lot of battery and charger information in this ECF sub-forum:
http://www.e-cigarette-forum.com/forum/batteries-chargers/546143-batteries-chargers-multi-meters-forum.html
Always respect the power that is in these batteries and always practice safe battery habits.
in their face blowing their teeth out and what not. My best friend's husband has a top of the line mechanical mod and they asked me to take hit to see the difference but they warned me not to hold the button too long because it would explode! So naturally I was a little apprehensive but still wanted to see what all the hype is about so I hit (but very quickly lol) and it was great! Although it it wonderfully and all do you think it's worth the risk? Do you think mechanical mods should even be outlawed or recalled for until the manufacturers to build them more safely? 
