Milk in the ductwork

We had this customer service rep who used to work for us.

I say that he used to work here because we fired him 2 weeks ago.

We had to. He was just terrible. He did things like flirt with the female customers and female coworkers, show up late almost every single shift, and he had really poor hygiene. I mean this guy just smelled bad all of the time. So, finally enough was enough and we fired him. However, about 2 days after he was fired we noticed a really bad smell start to develop in the office. People joked that the fired man’s ghost was haunting us. But that isn’t possible. We fired him. We didn’t kill him. Another day passed and the smell got really bad. It seemed to be coming from the HVAC vents. We had to turn off the air conditioner and use fans instead. That helped for every room except the customer service room. Finally, a local HVAC company came out and took a look at our ductwork. They found the smelly problem right away. Apparently the guy we fired put a small milk container in the ductwork before he left. He must have unscrewed the vent cover, placed the open container of milk inside, and then closed the vent back up. I guess he did this while cleaning out his desk. Whatever the case, it was intentional and gross. From now on, we will have to watch people clean out their desks before they leave for the final time. I don’t want a smelly HVAC system again.