It's important to know how pipe bombs work so you never, ever make one by accident.

A pipe bomb requires:

• An enclosure that's strong enough to hold a lot of pressure, with no way for it to escape
• Something inside the enclosure that produces even more pressure than the enclosure can hold

The way you avoid building pipe bombs is:

• Always be alert and wary when something can produce pressure (e.g. gets hot, changes state, or undergoes a chemical reaction)
• Don't enclose things in a way that might prevent pressure from escaping
• If you do, make sure there's a way for excess pressure to escape.
  • Provide an exit path or paths (such as the choke nozzle of a rocket engine. Make sure the path can not become blocked or thing through what happens if it does.
  • Provide a pressure release – a path that is initially/normally blocked but that will pop open well before the pressure becomes great enough to blow up. Your thumb on a bottle when you shake it up works this way. Think through what will happen if this fails.
• Remember to think through all the failure modes you can think of. What will happen if it does blow up? Inflating a (normal sized) balloon is reasonably safe because if you exceed the pressure and it blows up you have little buts of light weight plastic flying at you. Glass blowers making big glass globes have to worry about bits of molten glass coming at them. This is is why rocket engines are made of paper and not plastic or metal.