This thesis mainly deals with design fires in underground hard rock mines. The issue of design fires is an important part of the fire safety in underground hard rock mines. The first chapters provide a basic knowledge about design fires, the importance of design fires etc. The thesis aims to elaborate on the subject of design fires in underground hard rock mines. It also aims to supply tools for determining design fires in underground hard rock mines and to improve fire safety in mines in order to obtain a safer working environment for the people working for the mining companies in Sweden or for visitors in mines open to the public.