My brother who is currently a student at Aberystwyth University (my old uni) text me earlier today to tell me there was a fire at the National Library of Wales in Aberystwyth. I have a joint honours in English Literature and Welsh, and as a part of my Welsh language studies we visited a lot of important Welsh cultural institutions to talk to the staff about the role of the Welsh language there. The National Library of Wales was one of these, and I remember being terrified at the idea of being there when a fire broke out because of the tour behind the scenes.
The National Library of Wales is a copyright library which means that it holds a copy of every book or newspaper published in the UK. There are miles and miles of shelves behind the scenes and because many of the documents are very rare, they would be damaged by water sprinklers in the event of the fire, so they have air tight steel walls which come down before the room is pumped full of carbon dioxide to prevent the materials stored becoming fire damaged. I think a special alarm sounded to let you know that the steel curtains were coming down and you had a minute to get out. Really scary. At least you’d stand a chance of getting out of a burning building.
You can read more about the fire here