The threat to humans from a fire in a building to a large extent depends on the fire development during the preflash over period. In a fire heat, reduced visibility and toxic products will all at some stage threaten life safety. A long term goal for research activities in this field is the development of test methods from which the behaviour of the tested material or product in a natural fire can be predicted. This report is a summary of four reports (1), (2), (3) and (4) all dealing with different subjects of relevance to this long term goal. The reports summarized here constitute an integral part of a substantial research effort on preflash over fire growth and spread carried out within the national Swedish fire research programme as briefly outlined in (1). The report (1) is a short presentation of experiments in which therate of heat release (RHR) was measured for 13 interior lining materials.