Diesel Server
Back when I used to actually touch computers for a living rather than drive a mouse and keyboard I was the lead engineer installing branch servers for a British company that made oxygen
These were tower servers to support a windows 95 rollout. Most were installed in stationary cupboards with no special environmental.
I was called to go and check on one we installed a few weeks later as it has stopped working. It looked find from the outside so I disconnected the power and cables put it on its side and opened the side panel.
What erupted from wiring was a black sludge that came out 15-20 cm from the case. It was sticky and disgusting but also a mystery.
After talking to the office manager we found out the computer had been making the room too warm so the little windows had been left open.
I walked around the side of the building and the building was actually built into a hill side and parked with its exhaust pointing directly at the window was a lorry. Each morning and throughout the day 10-15 small trucks would park there and when they started their engines pump a black cloud directly through the windows. The computer was dead