Besides providing indoor living comfort, a building must also ensure the safety of its occupants. Natural disasters excluded, the safety of a building’s occupants is most often threatened by fire. More than one-third of all fires in the world are related to fires in buildings, and currently more than 10 people per million of the population die in building fires. Due to the constant updating of fire-safety regulations, the number of deaths due to fires in buildings has declined by 65% over last 30 years [1]. Building physics in the field of fire safety focuses on a description of the physical fundamentals of the fires in buildings and the way that building materials and structures respond to a fire. A fire in a building occurs in several stages. In the first stage, which usually takes for up to several tens of minutes and is known as the fire growth stage, it is important to protect people as they are evacuating the building. In the second stage, with a fully developed fire, it is necessary for the building structures to retain their load-bearing capacity and prevent the spread of the fire to other building zones or the surrounding buildings. Thus, extinguishing a fire is less dangerous for the firefighters and leads to less damage to property. The fire safety in buildings is achieved with both passive and active measures. The passive measures are related to building materials and the building construction’s response to the fire, while the active measures include the control of smoke and heat propagation in buildings by either the natural or forced ventilation of fire compartments. Other active measures include technical systems for detection, alarm and fire-extinguisher systems.