In the preceding issues, the visibility of the white light signs through smoke were reported. In this paper, the visibility of colored signs through smoke was studied. Smoke was generased by burning kerosene and various building materials such as wood, polystyrene and polyvinyl chloride. In case of smoldering smoke, the flaming was prevented by supplying an electric furnace with nitrogen gas.
As shown in Fig. 1, the spectral transmittance of fire smoke was measured with the combination of a smoke density meter and seven kinds of interference filters. The spectral transmittance was converted into relative spectral extinction coefficient as shown in Fig. 2a-c∼Fig. 8 a-c Generally speaking, immediately after smoke generation, the extinction coefficient of short wave light is larger than that of long wave light, The difference between these two extinction coefficients reduces with time, and such tendency is reversed itself after long time elapsed. The time of this reverse occurs depedns on the initial smoke density, and slightly on the kinds of building materials and the burning condition. Discussing of escape through fire smoke, the spectral extinction coefficient of the smoke after the long time elasped or that of the smoke with extreme higher density may be not so important.
In case the diameter of smoke particle is smaller than 1μ, the extinction coefficient of short wave light is larger than that of long wave light as shown in Fig. 9, While, in case the diameter of smoke particle is larger than 1μ, the extinction coefficient of long wave light becomes larger than that of short wave light (see Fig. 9). Accordingly, it is evident from Fig. 9, 10 and 11 that the reverse of the spectral extinction coefficient is due to the enlargement of particles.
Ratio of the visibility of red light V_RED to that of blue light V_BLUE calculated from Eq. (1) is shown in Table 1. The visibility of red light will be larger than that of blue light, i. e. by 20∼40% for smoldering smoke (White smoke) and by 20∼30% for flaming smoke (Black smoke).
In order to exend the visibility of signs in fire smoke, another probable method is to increase the brightness of a sign.

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Analysis and characterization on the process of combustion of organic materials including the flame-retarding ones were studied primarily for the objective of evaluating on the gain in the flame retarding potency of the newly developed γ -ray irradiated wood plastic composites (W.P.C) containing poly-vinylidene chloride.
For the stated purpose, the investigation was pursued by taking steps of studies in the following phases ;
i ) The simulation on the weght-loss of the samples in combustion-process by the linearized operator model including time constant (T₁, T₂) corresponding to tow characteristic (physical and chemical) resistances in a parallel circuit. The former (T₁) primarily concerned with time-constant in the heat-transfer and the latter (T₂) primarily concerned with the time-constant in the heat-evolution induced by chemical reaction during combustion-process.
ii ) Analysis on the respective data concerning the samples in the test-furnace and the estimation on the respective gains contributed by the presence of HCI from the thermal-decomposition of the flame retarding polymers in W.P.C :   Heat evolution in gas and solid phases, CO₂/CO ratio in combustion-gas, apparent activation energy (ΔE ) and frequency factors (A *) for the weight-loss rate of the samples and smoke-evolution potency (C₈^Max ).
iii ) The microscopic observation for the said contribution by DTA-and GC-data. Asaignment of the function of HCI from VDC and the synergistic function of the co-polymerized organic phosphoric acid compound (TAP). The expected place of polymerization in wood the roll of the respective monomers particularly AN.
Follwing results were obtained ;
I ) Linearization of the operator.
Φ_w (s )=I (s ) G (s ), I (s )=1/s, G (s )=K₁+K₂
K₁=α (1−αβT ²₁exp(−L_T /T₁)/T₂²) ⁄ (T₂s+α ),
K₂=(αβT₁²exp(−L_T /T₁)/T₂² ) (1+αT₁/T₂) ⁄ (T₁s +1+αT₁/T₂)
where α, β meant 1+ΔE (T_Max −T_R )/RT ∞² and (1−γ ) ΔE (T_Max −T_R )/RT ∞² respectively. T_Max, T_R, T ∞, R and γ maximum temperature in the sample, room-temperature, hot-bath temperature in the furnace, gas-constant and (T_∞−T_R )/(T_Max −T_R ) respectively. Φ_w (s ), I (s ) G (s ), K₁ and K₂ meant weight-loss curve as normalized by the initial weight Wo of the sample input function (step-input), transfer-function, resistance of heat transfer and resistance of combustion or heat-evolution respectively.
II ) The presence of the flame retarding polymers increased the heat-evolution in solid phases, However, prominetly decreased the heat-evoluton in gas phases corresponding to the presence of HCI with the pocket at 20% polymer loading.

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The characterization on the mode of combustion of organic-interior materials in JIS A 1321 type (ISO-type) test-furnace was pursued where the driving-force for the combustion was considered to be primarily due to thermal radiation. Following equation (I) was provided for the characterization on the basis of the experimental result ;
1⁄W₀ | (dW⁄dt)_av | = a_i I +a₀            (1)
where I was the radiation intensity (cal/cm² sec) as observed on the surface of the standard asbestos board in the furnace a_i and a₀ were the coefficient for the characterization and their physical meaning were given in equation (3). Equation (3) was derived from equation (1) in terms of equation (2) which had been derived theoretically on the basis of the balance of Reynolds flux through combustion interface (in the previous report (1)) ;
1⁄W₀ | (dW⁄dt)_av | = Sh (T_F −T_L )⁄2W₀Q (2−X ) + Sσρc_p β * g₀(T_F −T_L )²(1−X )⁄3W₀QV_F L₀(2−X )            (2)
1⁄W₀ | (dW⁄dt)_av | = I ⁄2ρQL₀(2−X ) + δρC_p β *g₀(T_F −T_L )²(1-X )⁄3ρQV_F L₀(2−X )            (3)
h = (h_R −h_c), a_i = 1⁄2ρQL₀(2−X ), a₀ = δρc_p β *g₀(T_F −T_L)²(1−X )⁄3ρQV_F L₀(2−X )
where heat-transfer coefficient by thermal radiation (h_R ) was assumed to be much greater thant the one by convection heat-transfer (h_c ), and the ratio of suface area of material to the weight or S/W₀ was put approximately equal to 1/ρL₀, β * was the volume-expansion coefficient of air and other notations were the usual ones as refered to the previous report. Since Iinear relation was recognized among a_i and 1/L₀ in a_i vs. 1/L₀ plot, 1/ρ(2−X ) should be held constant irrespective of the separate change in ρ and (2−X ) during combustion. The said evidence was numerically verified in the cross check on ρ and (2−X ) in the process of computer follow-up for the simulation of Ts and T in terms of equation (5) and (6).
Since 1⁄W₀ | (dW⁄dt)_av | was subjected to the rate-constant k of the combustion reaction, a_i should be related to k in terms of equation (1) which was represented in the decrease of the mean value of fluctuation change of ρ or ρ_av with respect time or temperature in the said simulation.
For the standardization the values of tdθ obtained at the vent-end of the furnace as the measure of heatevolution, following correction in terms of maximum gradient method was conducted for the estimation on the characteristic loss value of the furnace to obtain the true heat evolution ;

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