The toxicity factor, T, reported earlier^{1, 2)} was related to the total potential for toxicity production and, as such, does not consider time. Although two materials may show an equal value of the toxicity factor, however, the one that burns faster will create a greater toxicity hazard. In order to measure this difference, the concept of a “dynamic toxicity factor”, TD, is proposed based on rate of toxicity production.
Toxicity, t, the result of a gaseous compound, has been defined as t = c/c_f, where c is the concentration of the gas and c_f is the concentration of the same compound that is fatal to man in 30 minutes. When a material burns and produces an atmosphere of toxicity, t, the toxicity factor, T, of the material has been defined as T = tV/W, where W is the weight of material and V is the volume into which the toxic gas is dispersed. If c is expressed in terms of the partial volume, u, of the toxic gas, then T reduces to u/W/c_f.
As T is based on unit weight of material, it is comparable to the heat of combustion and the smoke generation coefficient³⁾. Recently, the rate of heat released and the rate of smoke generation, which may be called dynamic quantities, are considered more appropriate to describe fire hazard characteristics. Their counterpart in the field of toxicity would be a rate of toxicity production. As the rates ara normally defined or determined on the basis of surface area of materials, the present paper proposes to define the “dynamic toxicity factor” as the rate of toxicity production per unit area, viz, TD = ú/A/c_f, where ú is the volume of a toxic gas produced in unit time.
The value of TD for a single compound or a sum of the factors for two or more compounds can be determined by combustion experiments followed by chemical analyses of component gases. Some examples of data for white pine and a polyurethane foam are presented in Table 1. In the combustion experiments the level of irradiation was varied from 2.0 to 3.2 W/cm² and samples were burned or pyrolyzed under three different atmospheres of air, nitrogen and a one-to-one mixture of both. The rate was calculated from the slope of the central 80 per cent of the gas volume-time sigmoid curve. In this limited number of experiments the dynamic toxicity factor of white pine varied from 0.5 to 14.1 L/cm²/min; that of polyurethane variad from 1.4 to 2.3 L/cm²/min.
Present trends in the study of combustion toxicity are towards the use of animals. One type of experiment widely used is to decompose materials by surface irradiation and apply the pyrolysis or combustion products to test animals for a specified period of time. This experiment has some similarity to the determination of the dynamic toxicity factor. The factor TD would be useful in planning an animal experiment of this type, and could predict the result of animal experiments so that fewer such experiments would be necessary.
As the toxicity factor and the dynamic toxicity factor are built on a common base, most of the merits and shortcomings of the former are applicable to the latter.

抄録全体を表示

Infrared extinction spectra in the 2-12 μm region have been obtained for smokes of wood, polystyrene foam, polyvinyl chloride and kerosene.
Spectra were found to depend on smoke generating condition (smouldering of flaming) rather than on the sort of combustibles. In the 2-5 μm region, extinction coefficients for white smokes from smouldering solid combustibles were inversely proportional to the cube or fourth power of wavelength, while those for black smokes by flaming combustion were approximately proportional to the inverse of wavelength. In the 5-12 μm region, the extinction characteristics showed some irregularities probably due to selective absorption by water vapour and other gaseous combustion products.
Experimental results with smouldering smokes were compared to calculated extinction characteristics based on the Mie theory to estimate smoke particle sizes. These were, in diameter, 1.2-1.3 μm for wood, 0.6-0.7 μm for polystyrene foam, and 0.7-0.8 μm for polyvinyl chloride, and were in good agreement with values formerly obtained by sedimentation method.

抄録全体を表示

In order to protect our cities from the earthquake-fires, it is necessary to study on the outbreak of fires.
At first, in this papers, it is explicated that the fire risk of fire-tools for heating is larger than that of fire-tools for cooking and bath-boilers.
In this study, fire statistics of usual-fires and records of earthquake-fires are used for analysis and processed statistically.
Secondarily, the problems of early extinguishment in the earthquake-fires are discussed.

抄録全体を表示