[rommelvr]

The amount of times my friends and I made pressure bombs (in a 600ml bottle) using NaOH and Al (exactly what was described in the article, and frankly, my first thought when reading this) at school and at home I can't even count on two hands. It was initially shown to us by our Chemistry teachers as a method for creating H2. The real danger isn't the expanding/produced hydrogen, it is the highly basic solution that is still reacting within the bottle. If you're nearby, and it explodes, depending on your volumes, the resultant spray can be seriously ... painful. Safety goggles and a nearby water source is a must have. Been a few times where I've rushed to the shower after my face started bleeding from corrosive spray after a mis timed attempt at this... If she was just capturing the hydrogen and igniting it... then it was completely harmless.