Characterization on smoke evolution of organic building materials in fire have been pursued with respect to the change in dissymmetry factor Z in light scatterring data.
The change in dissymmetry factor Z has been recognized to be very sensitive to the change in radius of smoke particle by the secondary oxidation in hot environment and above change in Z induced by the change in radius of smoke particle have been also recognized to be influenced by the change in particle size distribution.
Theoretical consideration on the data concerning the change in Z factor, electro-microscopic observation and Royco Particle Counter analysis of smoke particle evolution under respective oxygen partial pressure will suggest that the change in turbidity dC_s/dt in the previous report (Part I) will be mainly due to the change in particle number dN/dt which will depend on thermal decomposition rate dW/d_t of organic materials at high temperature.

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This paper is concerned with the effect of different smoke, as well as of smoke movement, to the response characteristics of smoke detectors. The method is employed essentially the same test fires as those performed by TH Aachen and UL. The fuel is selected bearing Japanese fire statistics and other test fires in mind. In this report, a smoke density is indicated by the extinction coefficient per meter for natural logarithm.
The results are summarized as follows :
1) The general tendencies of effect of different smoke to the response characteristics of smoke detectors are mainly obtained by 7×7×2.7m small room tests :
Light scattering type detectors operate at the rated smoke density for cellulosic smoke, and at a density equals to 4 times as dense as the rated density for sooty smoke from burning kerosene and polystyrene, and intermediate density for smouldering cellulosic smoke.
Ionization chamber type detectors are sensitive to flaming combustion, and insensitive to smouldering smoke. It is noted these detectors operate by transient masses having an abundance of invisible combustion products in the moment cellulosic strips flame up. Smoke density at the time of operation of a certain detector is very higher value than the others because of the difference of construction.
A detector sensitive to water vapour in smokes operates by cellulosic combustion products and by even those of alcohol, but does not detect those of plastics.
A few fixed-temperature type thermostats having very short thermal time constants are still more insensitive than rate-of-rise type thermostats.
2) For the purpose of getting effect of movement of smoke experiments are performed in a building having 20 m corridor and stairway extended over 3 stories.
Smoke density at the time of operation of detectors increases, the farther the distance from a origin of a fire is.
3) For small room tests, the mean vertical velocity of smoke is found to be between 20-180 cm/s, and the mean horizontal velocity between 5～150 cm/s. For the larger scale tests, the velocity of smoke front in corridor is observed to be between 1.3～14 (average 4) cm/s.
4) A physiological limit with smoke exposure will be set at smoke density of 0.02/m for cotton fires,0.28/m for wooden fires,0.72/m for gasoline fires.
5) By the smoke box tests under laboratory condition,it is found that ionization chamber type detectors can operate when PVC is heated at a temperature above 240°C in a humid atmosphere,and at a temperature above 300°C in a dry atmosphere.
Further studies on smoke particle size distribution and on the physical properties are needed to illustrate unstable relation between smoke density and the output of detectors. In order to produce more successful results, it is necessary for test fires to improve the method of ignition and the promotion of combustion and to select fuel.

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(1) The fire spread formula of forest of Kure city with 230.000 persons is shown by the following equation (1).
   A＝(0.34σ +0.26υ+0.23)x^1.34      (1)
A : burned area (a), x : time (min), υ: wind velocity (m/sec), σ : standard deviation
(2) The formula of number of firemen for forest fire of Kure city is shown by,
   P＝9.84 A^0.430            (6)
P : number of fire men for forest fire
(3) The formula of number of fire engines for forest fire of Kure city is shown by,
   P_f＝1.95 A^0.344            (7)
P_f : number of fire engines for forest fire

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Analysis on the surface flame-spread velocity of plywood in the inclined tunnel-furnace has been pursued with respect to various inclination-angle and flow-rate of the fuel-gas. Following theoretical equation has been derived as a particular solution for the stationary state surface combusion ;
V_f=ρC_pV_fa/3Lρ_ωC_pωτ +L(h+h_avR)/2ρ_ωC_pωτ(2－χ)+aρC_pβg₀ sinθ(1－χ)(T_F－T_L)/3ρ_ωC_pωτV_F(2－χ)
where V_f  and V_F  are the mean flame-spread velocity and hot current velocity respectively, L and a are flame-lenghth and thickness (δ) over L as the parameter concerning the-shape of flame, h and h_R are heat-transfer coefficient by current and radiation respectively, T_F and T_L are the temperature of flame and surface temperature of sample at the top of flame, χ and τ are the heat-loss coefficient and thickness of sample, _ρω and C_pω are the density and specific heat of the sample, ρ and β are the density and volume-expansion coefficient of air. The first term on the rightside of the above equation concerns with the drafting effect of the hot current velocity (V_F), the second term represent the radiation-effect by the flame-lenghth, and the third term expresses the contribution from buoancy-effect of the current. The initial driving force to propagate fire from small fire-source from wall to ceiling is considered to be due to the third and second effect and the succesive increase of the fire-source on the floor will accelerate the drafting-effect of the hot-current exponentially as are represented in the first term of the equation and then reaches to the so-called flash-over.

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