Full scale fire test was performed in Yokohama from 14th to 16th, Sept. 1964, with a view of finding the following factors :<br>(a) The difference of the development of the fire in rooms which were finished by different internal linings .<br>(b) Smoke discharge test for the smoke tower (18m×18m) which was installed adjoining to the stair-case.<br>(c) The development of the fire in a large office room whose opening is very small and whose ceiling is covered with treated acoustical perforated fiberboards.<br>The building used for the test was of 4 stories and was to be destroyed soon after the fire test.<br>The results :<br>(i) The difference of the development of the fire in rooms which were finished with different internal linings, were very similar to that of the fire in a small model compartment. In the room finished with untreated plywood board, the period from ignition to flash over was about 4 minutes and this was the minimum value of the flash over-time. In the room, finished with treated plywood board, this period was about 6 minutes and in the room finished with plaster board, the flash over could not be seen this time.<br> (ii) The smoke tower discharged the smoke very well from the stair-case this time. This is thought to be due to the following two facts :<br>(1) The air-current which contributed to lead the smoke into the tower, was made up by the air which came through the opening of the entrance, located at the lowest end of the stair case. This current went up along the stairs and entered into the tower. The importance of the existence of an inlet of the air in the building was recognized now.<br>(2) In the room next to the stairs, the door between the stair-case and this room, was located on the lower part of the wall, while the opening to the smoke tower was located on the upper part. This enabled to form the draught from the door to the opening in this room and contributed to lead the smoke to the tower.<br>Though the tower was very useful this time, further careful considerations will be necessary for the tower in a very tall building.<br>(iii) In the full scale fire test which we had in June 1961, we ignited in the room (32.7m×7.1m×3.6m) which was very similar to that of this building (21.0m×8.0m×2.5m), but whose openings (total area 21.6m²) were not so small as this room (total opening area 5.8m²). At that case, the fire spread in the whole of the room in 3.5 minutes after ignition and grew up to a very heavy fire which we had never expected. This time the fire was very powerless and we had to ignite again 25 minutes after the first ignition. After the second ignition, the fire front progressed very slowly toward the openings and when it drew very near the openings, the fire suddenly became active and the fire men started fire extinguishing.