To delay the invasion of smoke to prevent generation of a section surrounded by smoke by making protruding amounts of dangling walls to partition a section important for guiding evacuees and orderly decreasing protruding amounts of the dangling walls as becoming more distant.

Dangling walls 41-47 are classified into three kinds of protruding amounts H1-H3, which are H1<H2<H3, and H1 is a value not lower than a legal regulation (50 cm). When a fire broke out at a section 50 to generate a large amount of smoke over a smoke eliminating capacity, smoke fills under the ceiling face of the section 50. When the thickness of the smoke came over H1, the smoke comes under the dangling wall 42 to diffuse in a section 48. When the thickness of the smoke in the section 48 over H1, the smoke comes under the lower dangling wall 41 in the section 48 to diffuse in a section 49. When the thickness in sections 50, 48 and 49 came over H2, the smoke diffuses in the section 51 and 52. When the thickness of the smoke in the sections 48-52 came over H3, the smoke comes under the dangling walls 46 and 47 to diffuse in the last section 53. All the building is filled with the smoke at last.