This report aims at summarising the main features of the studies carried out and rough conclusions from these. Initially a short description of a number of relevant concepts is given after which different problem areas are addressed. One example of the latter is fire in more or less sealed compartments and how these can be characterised in terms of pressure rise due to thermal expansion etc. In the remainder of the report, focus is on fire- and smoke spread in ventilation systems, which constitutes a complex area of fire safety engineering and planning. Further a description of different test methods (air leakage test and Hot Smoke Test) for evaluating the protection against smoke spread in existing buildings and installations is given. Finally some suggestions to future research activities within and in association with the area are given.