Section C door code

[espresso]

Well i have same problem looks like but still cant find answer lol

Spoiler below!

I found a blank note in shaft 13. I found closed door in shaft C. And u say i have to go to shaft 12 to use blank note on UV light but i cant cause door to it is closed! so only where i can get in is some kinda of oil plant room, close to shaft 12. and what to do there? i go ahead and i see big ventelator upstars, also an attached ladder but i dont know what to do there!