The little batteries that come with the stock little electronic cigarettes are all Lithium-Ion batteries, and if they were to blow, you would get a little pffffft sound and it might leak some battery juice.
But I don't remember hearing of that happening.
Now when you get into the big boy batteries on the mods, then you do have some reason for concern. First you need to make SURE that you get
protected batteries. And if you are super-hardcore worried, then you should get a mod with vent holes just in case.
But if you get protected batteries, you will almost certainly never need the just in case.
And I always leave my batteries charging over night.
Including the big boy 18650s I use.
But I do put the whole charging system in the bathroom sink just in case.
