Well Thank you, Mr. Thornton! I made a lot of researchs, and I found that, the NKB Levels (Nordic Regulations on Fire Safety in Buildings) is nothing more than a set of regulations on design of buildings / buildings where action will be taken in case of fire, ie, have structures that must be followed to obtain better performance in case of fire.
I'm trying to attach a file but it's too large, send me your e-mail, sure I can send u materials of my research
Best Regards