The distributions of the floor factor ( F_f )( floor area/total area of inside surface )and of the temperature factor ( F_o ) ( air flow factor/total area of inside surface ) in about 30 buildings which have been examined previously (KAWAGOE, SEKINE, B. R. I. Occasional Report No. 11,1963) are shown in Fig.1 and Fig.2.

When limitations of factors are taken as follows, the equivalent fire duration obtained by the nomograms proposed previously ( KAWAGOE, B.R.I. Research Paper No. 29,1967 ) are shown in Table 1, Fig.3 and Fig.4.

It may be said that the equivalent fire duration depends remarkably on design of room and it changes widely from 20 minutes to 130 minutes where the fire load is 50 kg/m² from 35 minutes to more than 200 minutes where 100 kg/m²

* Manuscript received on December 2, 1970
** Director of Building Research Institute, Ministry of Construction