When responding to fires in buildings, knowledge of fire gases, the spread of fire gases, pressure conditions and ventilation measures can often be decisive to the results of the operation. This book describes basic principles for fire ventilation and the spread of fire gases, how fire ventilation can be carried out, positive pressure ventilation and the possibilities and problems that arise in connection with creating openings in different types of structures. The book provides examples of a number of situations and also a general reasoning about tactics with respect to fire ventilation. The book is primarily intended for training activities, but is also aimed at active firefighters and other interested parties.