I was a Teach For America corps member at the time, so a staff member from the regional office was coming to observe me that fateful day. It had been unusually cold for south Texas--amazingly, although it was towards the end of the second winter I had spent down there, it was the first time I had ever had to turn on my classroom heater. As I did so, it started making weird, rackety, banging sounds. I was sort of alarmed, but I kept on teaching.
All of a sudden, smoke started coming out of the heater vent and a horrible stench filled the room. The heater was on fire! But, wait! It wasn't the heater that was on fire; it was the dead creature shacked up inside it that was burning. Ick. In response to the rancid odor, several of my students promptly vomited. All this just a short while before I was going to be observed.
We dealt with the odiferous situation by shutting off the heater, spraying tons of Febreze in the air, opening the windows to let fresh air come in, and chilling in the abandoned teachers' lounge at the end of the hall until the room was habitable again. Luckily the stink cleared out quickly, and we were able to go back in the room by the time my program director arrived to observe my class. I've always wondered if he noticed a funky smell, though...