In this paper we report the experimental study on the flow of smoke and air in the model anteroom in case of large air inlet and smoke outlet openings which open from floor to near the ceiling and from ceiling to near the floor respectively. The result was compared with the field experiment of similar openings and was made some supplementary discussions.
The model and the apparatus used in this experiment are the same as in part 2, except openings. Moreover, the condition of similarity assumes the same as in part 2, that is, the ratios of supply air and inflow smoke volumes to anteroom volume are equal between model and prototype, therefore, the flow l/s for the model corresponds to m³/s for the prototype.
In this experiment following results are obtained.
(1) Flow characteristics of smoke and air in the anteroom, under constant volume and optical density of inflow smoke change continuously with supply air. This flow characteristics were classified, in parts 1 and 2, to types O, A, B, C, D and E. However, in this experiment they were classified to types O, A′, C, D and E. The two layer flow was consisted of types A, B and C in parts 1 and 2, and of types A′ and C in this case, so the type B which has fully transparent lower layer was not formed. This shows that the openings of this type is inferior to those of parts 1 and 2.
(2) The limits of supply air volume keeping up to two layer flow are very different from those of parts 1 and 2. The upper limit descend and lower limit ascends with increasing smoke volume, moreover, when smoke volume exceeds 6 l/s two layer flow are not formed.
(3) The relation between mean boundary height and air smoke ratio in two layer flow coincide fairly with that obtained in part 2. The mean boundary height determined by observation agrees fairly with height estimated from temperature profile, and very well with height estimated from optical density profile.
(4) Being based on the flow characteristics of the model experiment, the results of field experiment are reexamined. Consequently, fair agreement is shown between the mean boundary heights in the model and in the field experiment with similar openings.
(5) Characteristics of temperature profile for types O, A, C, D and E do not differ markedly, so that the classification to types by temperature profile is very difficult, however, distinct classification is possible by optical smoke density profile.
(6) According to conclusions (1), (2) and (3), it can be concluded that the case of air inlet and smoke outlet openings shown in this report is the worst. Better is the case of openings in part 1 which are air inlet in lower part and smoke outlet from ceiling to floor, and the best is the case of openings in part 2 which are air inlet in lower part and smoke outlet upper part of the wall.

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Experimental studies were made of the diffusing behavior of LPG (liquified petroleum gas) on its leakage into the flowing air over the flat ground. A small wind tunnel with a cross section of 40×40 cm² and 3.6 m in length was used. Its wind velocity was variable from 0 to 3 m/sec.
As a sample gas, carbon-dioxide was employed instead of propane for the sake of experimental safety, while they were similar in molecular weight and, accordingly, in specific gravity.
The sample gas was let to leak out onto the floor of the wind tunnel through a rubber tube, 10 mm in diameter, and the concentrations at points in the leeward layer were measured by means of an interference gas detector and a recording type infrared gas-analyzer.
The rate of leakage was varied from 3 to 18 1/min, and the wind velocity from 0.13 to 2.0m/sec. Summarized are the results and conclusions as follows :
1. The ejected gas was observed to diffuse in a form of creeping layer over the floor, leeward from the leakage point. The gas concentration close to the floor-surface decreased exponentially with the distance from the leakage point.
2. The width of the downwind gas-layer decreased rapidly with the increase of wind velocity, provided the rate of leakage was kept constant, while the thickness of the layer showed a slight increase as the wind velocity increased.
3. Contours of the gas concentration are as illustrated in Fig. 16, 17. The manner in which the rate of leakage and the wind velocity affected the pattern of gas-concentration distribution was examined.

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This report includes the discussion about the relationship between the range of explosion for the fuel-air-dry powder system and the extinguishing effectiveness of dry powder against fires of various liquid fuels.
The range of explosion was measured by the apparatus shown in Figure 2. The extinguishment was effected using the apparatus shown in Figure 3. The former′s results are summarized in Figure 4, and the latter′s in Table 2.
Through these results, it is concluded that the mixture of fuel-air does not explode, when the sufficient dry powder of concentration P (P is a peak concentration, g/l) disperses in the mixture. Similarly, the flame goes out, when the dry powder of concentration P/(1-c) (c is a fuel concentration in the fuel-air mixture at the peak concentration) disperses in the surrounding air. Further, the minimum necessary discharge rate E (g/min) is expressed as :
E=(P/ｃ) · V=(P/ｃ) · (22.4/M) · W=(P/c) · (22.4/ M) S · V · _ρ    (1)
where, V is the gaseous fuel volume evaporated or discharged in unit time (l/min), M the molecular weight of fuel, W the fuel weight evaporated in unit time (g/min), S the surface area of tub (cm²), the burning velocity of fuel (cm/min), and _ρ the density of fuel (g/cm³), respectively
In the extreme right column of Table 2 is given the ratio of experimental value of discharge rate to the value calculated by the equation presented in footnotes. Three cases ware discussed in order to explain the ratio being greater than unity.

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An investigation on the extinction with water sprays of fires of liquids burning in cylindrical vessels has been carried out. The blow-off tests by the wind sent from the right above position of burning liquids have also been carried out to clarify the effect of the air-flow in the spray on extinction. Eleven vessels of various dimensions and sixteen different liquids were used. Sprays were produced from six swirl nozzles and two impinging jet nozzles. Through these tests, the following two mechanisms are suggested to account for the blow-off :
1) dilution of the flammable vapor from the liquid to a concentration lower than that required to sustain flame ;
2) cooling the liquid surface when the stable flame as shown in Fig. 9 is formed.
As the mechanism of extinction by means of water sprays are considered the following factors in addition to the above-mentioned mechanisms of blow-off by the entrained air :
3) dilution of the vapor layer by the formation of steam at the flames, vapor zone, vessel wall and liquid ;
4) cooling the flames, vapor zone, vessel wall and liquid by the formation of steam and by spray drops
5) for the water-soluble liquid, dilution of the surface layer to the concentration where the liquid is no longer flammable.
The extinction will not occur by any single factor of those mentioned above but by the combination of some of them.
When the preburn time is short and the depth h of the liquid surface below the edge of the vessel wall is large, the stable flame which will not easily be blown off is formed with such liquids as gas oil, ethanol, dioxane etc., whereas, at long preburn times and small h, the vapor zone becomes thick and the fire can be extinguished in a very short time (within 5 sec), by applying the wind faster than the critical speed, due to the dilution of flammable vapor. The fires of such liquids as gasoline, benzol etc., the vapor layers of which are thick from the start of ignition, are likely to be extinguished quite rapidly by the dilution of the vapor zone above the critical wind speeds which are greater than those of the former liquids. The fire is extinguished at the lower entrained air velocity with fine sprays than with coarse sprays. The extinction time for the water-insoluble liquid and the average concentration at the moment of extinction for the water-soluble liquid are mainly dependent upon the drop size and the entrained air velocity.

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