Reply to post:

I work school IT.

I was in a primary school once and got a call.

"What should we do if the printer is smoking?"

Although alarm bells did go off (in my head at least), there are certain classrooms where the printer is in front of a bright window in the morning, and the heat-vapour from the warm-up, plus the evaporated water from damp paper makes it look like wispy clear/white smoke is coming from them. The printers actually came with a manufacturer's sticker saying that it was normal and expected.

"What colour is the smoke?" I ask.

"It's like... black and smells of fire."

"Er... I think your printer is on fire, could you unplug it immediately?"

"Well, I'm waiting for my job to come out still."

Turned out, when I literally RAN to the classroom after a few seconds of "UNPLUG IT!" down the phone, that it was actually on fire. There was a heated roller at the top of the printer near the paper exit. When the paper exit was blocked, the paper would curve back on itself, re-enter that roller underneath and form an infinite paper loop of doom.

The printer was unable to detect that condition, and so would keep printing, wrapping more and more and more paper around the mummified roller, and keep heating. By the time I got there, there was a centimetre-thick layer of black, charred and quite obviously smoking paper wrapped in a perfect, compressed roll (almost ashen in texture when we later extracted it).

I hate to think what would have happened if someone hadn't been watching. Not least because the REASON the printer managed to wrap the paper in the first place was a huge stack of papers and books on the top of the printer blocking the exit path. And the reason the roller got hotter and hotter was that either side of the printer were... huge stacks of papers and books literally suffocating the side and rear vents.

We changed those printers, but not before HUGE warnings about not blocking the vents and exits like an idiot.

The only equipment I've ever seen actually catch fire, though, was a 10-year-old PC in a learning support department that... well... basically just decided to go up in flames for no reason whatsoever. The PSU just went pop, lit up and flames came out the back. The PC was so old that I didn't even try to diagnose the black charred mess, though, and binned the whole thing immediately. Again, just lucky people saw as the power didn't stop and the flames would have just caught other things if it had been allowed to continue.

I've also had Ni-Cd/NiMH battery chargers in a classroom (left overnight with two 9V batteries in them) go bang and spray acid over the entire carpet area where children normally sit in the mornings. Fortunately, it happened during a break time. The school banned all classroom charging after that.

Apart from the first story, though, there was literally no warning or anything we could have done to prevent it, everything was PAT-tested or in good condition and there was no indication of impending failure of the PSU/battery or anything else, and it was just sheer luck that saved us.

There are more than a few reasons that you need to be able to evacuate (herd) 500 children out the door in under two minutes, however, and practice it regularly. If you've ever seen a good fire evacuation in a school they are astoundingly impressive given the clientele being managed (e.g. two people gathering 20+ nursery-age children in seconds).