This is the biggest mistake I've ever made at work, and I don't think I'll ever be able to live it down.

I work at a large office building with several floors. A few months back I was trying to make popcorn in the microwave in the break room during my lunch break. I must have left it in for too long because suddenly smoke started pouring out of the microwave and the fire alarm went off.

I panicked and didn't know what to do, so I just ran out of the building like everyone else. The fire department came and it turned out to be a false alarm, but everyone had to evacuate the building and wait outside for over an hour.

To make matters worse, it turns out that the smoke from the popcorn had set off the sprinkler system on the floor above us, causing water to flood down into our office. My boss was livid, and everyone in the building was talking about the popcorn incident for weeks afterward.

I had to apologize to my coworkers, the building management, and even the fire department. I'm lucky that I didn't get fired, but I'm still embarrassed about what happened.

TL;DR: I set off the fire alarm at work by burning popcorn in the microwave, causing a false alarm and flooding the office with water.