The problem involved in determining smoke density data are described, inter alia, in the relevant national and international test methods. An attempt is made to illustrate general conditions for risk-related, application-oriented testing and assessment based on the possible obstruction of rescue work in the event of a fire occurring. The informativeness of such smoke measurements is explained. The influence of superficial fire propagation must also be taken into account in the interpretation of both static and dynamic methods. A static method such as the ISO smoke box method makes it possible, for example, to assess the effectiveness of screening facings and thus of the amount of time available for rescue operations before the exposed building product contributes towards the smoke generated per unit area.