In this chapter, the authors consider the aspects of fire and fire safety design with which the people need to be familiar: Ignition, development and spread of fire, Fire performance of construction materials and Design for fire safety. Phases of fire development are used to describe the life of a fire from its ignition to its decay. The guidance in this chapter provides a base from which fire safety can be included in the design risk management process. The fire performance of construction materials can be classified by two different characteristics: a material’s reaction to fire and its fire resistance. The guidance on fire safety in this chapter has been produced to bridge the gap between technical guidance with which designers will be familiar – including Approved Documents and British Standards – and the principles that underpin fire safety in buildings.