RR Donnelley had a place here in town which is now some other company and they are on the ropes. When I moved here 20 years ago they brought in paper stock by the train load. The internet sure killed the business. Man, we had some good fires there too. Usually in the bindery where they cut pages apart. All the scrap was vacuumed into a baler, there were several balers. Think like a shop vac with a 16 inch hose. The "filter" was what usually caught fire. A spark would get into the scraps and with the dust it would go pretty fast. The balers had sprinkler protection in them but where the filters were at was up top so we would have to open them up to get water on it. The filter box was 12 or maybe 14 feet cube and had "socks" stretched over wire cages. Worked just like a shop vac. Now picture your shop vac after running for a year and that was how the filters looked. It had valves on inlet and exhaust so they could cut the air supply off to it and it would go into the slow smolder mode. But it was still on fire and needed to get put out so they would call the fire dept and that was how I ended up there.
I remember being on top of the box once when one of the guys opened the access door. Like 2 feet square 1/8" steel sheet and hinged. When he opened it a little flame came out and he slammed it closed which knocked a whole bunch of dust loose from the filter. You think grain elevators can explode from dust, well a giant shop vac can too. It tore the hinges off the door and blew it across the room. I was on top shoveling down burning paper scraps to the guys on the ground 25 or so feet below. They were hosing down the burning stuff. The top lifted me up to where I hit the ceiling with my helmet which knocked years of accumulated dust off the ceiling and top of the machine. It got uncomfortably hot for a few seconds. That was the first time I was sure I was toast. Loud, hot and fire all around. I was geared up and the only real injury was my ears, they were ringing like crazy.
The guys on the ground were watching out for us up top though and they opened up a 2-1/2" hose and played it on the ceiling over the baler and cooled everything off fast. I never even got down off the baler until I ran low on air. I still remember my LT's smile when we got outside and took our masks off. "That was freaking cool. Let's remember that for the next time so we don't do it again!" Good times.