Bulletin of Japan Association for Fire Science and Engineering

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A smoke chamber is designed to perform the measurement of visibility through fire smoke (see Fig.3). The chamber is provided with an illumination apparatus and two kinds of sign. One of the signs is the placard and the other is the lighted sign which is backlighted with a projector. The brightness of the lighted sign can be controlled freely, and that of the placard can be set in four stages. Nearly white smoke is generated by heating filter-paper in an electric furnace.
Experiments were performed to get the relation among the brightness of sign, the visual distance, and the extinction coefficient of smoke in the instant of obscuration threshold. In this case the distances the between observer and the object were 5.5 m, 10.5 m, and 15.5 m.
The extinction coefficient (σ) in the instant of obscuration threshold may be theoretically given by
σ≒1/V ln B_E0/δ_ckL ………(1)
where V ; Visual distance
B_E0 ; Brightness of sign
δ_c ; Threshold of brightness-contrast (δ_c≒0.01 under the condition of general illumination)
L ; Intensity of external light (Illumination)
k=σ_s/σ (Ratio depending on the nature of smoke, k≒1 for nearly white smoke)
σ_s ; Mean light-scattering coefficient
From Eq. (1), the extinction coefficient in the instant of obscuration threshold is logarithmically proportional to the brightness of sign for a given smoke (nearly white smoke), a given intensity of external light, and a given visual distance. If the dimensionless brightness (B_E0/L) is constant, the relation between σ and V is given by
σ · V ≒ const.
The results of experiment are shown in Fig.4～Fig.12 The agreement between the results and the theoretical values calculated from Eq. (1) concerning the brightness of sign is good as shown in Fig.11. The visibility of the placard is about (2～4)/σ and that of the lighted sign is about (5～10)/σ.
In the case of escape through real fire smoke, the visibility should be lower than that of experiment, because the effects of physiology and psychology must be considered.

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Investigation on the mode of violent ignition of Japanese Lauwan plywoods with thin surface veneer and developments of flame-retardant, self extinguishing plywoods with untreated surface-veneer have been pursued.
Estimation on the particular temperature-profile along the glue-lines and inside the core have been pursued by I. B. M. 1620 computer on the basis of non-linear Fourier eq. involving Arrhenius terms.
Particular, extremely high temperature-profile along the first glue-lines have been recognized in the numerical computation just before ignition and inside the core upon heating.
Flame-retardant action of ammonium bromide and organic bromine compound immersed in the core have been recognized as negative catalyser in the vapor-phase combustion with respect to the core-treated and surface-untreated self-extinguishing plywoods.
Flame-retardant potency of the above material have been attributed to the percent of the suppression of heat of combustion ΔH₀ of woodmaterials. The reduced ratio of heat-suppression as represented in terms of ( ΔH₀-ΔH ) /ΔH have been linearly proportional to the logarithm of the concentration of ammonium bromide or its chemical potential in the vapor phase.
The reduced ratio will give 1 Kcal / mol as heat of combustion for the treated system from q=-32 cal / gr in the untreated systems.
The temperature profile experimentally obtained for the treated plywood has been perfectly coincided with those obtained in the numerical computation on the basis of Fourier eq, taking q equal to 1 cal / gr and E equal to 37 Kcal / mol.

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