It's embarrassing enough when you accidentally set off the fire sprinklers during a chemistry class, and even more so if you're the teacher.
But that's what happened to this poor chap when he decided to try and impress his pupils, but ended up evacuating the lesson.
One pupil at Glasgow High School in Kentucky caught the whole darn thing on camera, much to our pleasure.
To be fair to the teacher though, he did get a round of applause from his pupils - so not all bad.
Scroll down to the bottom of the article to view more chemistry experiments gone wrong.