Caipiranha: an explosive cocktail

Piranha solution is not a subtle way to get rid of annoying people (at least not yet :p ), but a mixture of hydrogen peroxide and sulphuric acid, and it is commonly used to clean samples.
The simplest recipe that I was taught was the following: put in a glass a certain amount of sulphuric acid, then pour hydrogen peroxide till it starts smoking.
You can now understand why it is called "piranha"..

Some time ago, CSI (Crazy Scientist Indeed) and his Ph.D student IKE (I Know Everything), were in the clean room preparing piranha. IKE has a bachelor in chemistry. After using the solution to clean their samples, while it was still warm, IKE put it in a piranha waste bottle which was already half full....and tightily closed the lid....
BOOOMMMMMM!
After a few seconds the bottle exploded. Luckily they both had moved away and the piranha reched only CSI's trousers.
The clean room was evacuated for almost a week and remained smelly for a month.
And if you come and visit us and look at the ceiling you can still see the trace of the explosion..

So, what can we conclude?
Two things:

1- Always be careful with waste bottles, and leave them degassing before closing the lids
2- Bad grass never dies