ANY BATTERY has the potential to vent hot gas when they are abused or used improperly. Some can actually go up in flames or explode, depending upon their chemistry.

All vaping explosions are caused by a chain of design errors, user actions, and possibly a battery fault.
- Mechanical mods, by their minimalist design, are more dangerous than other e-cigs.
- Sealed metal tubes (in a mechanical mod) 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 coils lower than 0.2 ohm will raise the amp draw exponentially and this increases risk - the power graph shows a significant change 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 - you need 30 amp batteries of guaranteed high quality.
Educating yourself, choosing the right batteries for your application, choosing a battery holder designed to be safe, and practicing safe battery habits greatly reduces the chance for a bad vaping accident.
LiPo batteries, like
ICR (Li-Ion), are not a safe chemistry battery. They can burst into flames and possibly explode when they go into thermal runaway. LiPo's are being used in a number of regulated mods, eGo batteries, and cigalikes that use an internal non-removeable battery, but they depend upon a PCB (protection chip) in their processor to be safe to use for vaping.
AAA over-the-counter batteries are I believe
alkaline chemistry batteries. Not a safe chemistry and don't have the current (amps) necessary for e-cigarettes. So forget about using them to power an e-cigarette.
The safest batteries for vaping are
IMR (Li-Mn) or
IMR/hybrid batteries. They are high drain (current/amps) and safe chemistry. They may still vent hot gas when they fail, but are not volatile or explosive unless the device they are used in does not have adequate ventilation holes.
Battery Basics for Mods: Ultimate Battery Guide
Deeper Understanding of Mod Batteries