AbstractA new concept for the storage of granular propellants envisages storage buildings that consist of a number of storage rooms arranged side by side, and which avail of a common entrance room. In order to examine the possible spreading of fire from one storage room to another during the deflagration of a propellant charge in one of the rooms, a number of deflagrations have been conducted in a experimental building which consists of three adjacent storage rooms and one common entrance room. The building itself is equipped with a valve‐type roof whose corrugated sections pivot on one side. The steel doors leading from the entrance room into the storage rooms are of the lifting‐type and are fitted with a dual labyrinth seal and an interspace ventilation.The middle storage room was used for 13 deflagrations of propellant charges ranging from 500 kg to 4500 kg. Four types of propellants of differing brisance were employed for the task. The measurements of the effects caused by deflagration upon the two neighbouring rooms and the surroundings of the building itself entailed considerable technical efforts. In virtue of the extensive test results the new storage concept is assessed as being safe.