=Danger from Gaseous and Liquid Fuels.=--All combustible gases or vapors, when mixed within definite amounts, are explosive. The violence of the explosion will be in proportion to the volumes of the gas and the condition of confinement. When gasoline or other volatile fuel is vaporized in a closed room, there is danger of an explosion, should the mixture of the vapor and air reach explosive proportions. It is dangerous to enter a room with a lighted match or open-flame lamp, where gaseous odor is markedly noticeable. In case of danger of this kind the windows and doors should be immediately opened to produce the most rapid ventilation. In the act of igniting the flame in a gas or vapor stove, the lighter should be made ready before the gas is turned on. Explosions in gas and vapor stoves are usually due to carelessness in igniting the fuel. It should be kept constantly in mind that, if a combustible gas is allowed to escape and mix with air in any space and then ignited, an explosion of more or less violence is sure to occur. Gasoline and kerosene are lighter than water and will float on its surface. The flames from these oils are aggravated when water is used in attempting to extinguish them. The burning oil floating on the surface of the water increases the burning surface. Burning oil must be either removed to a place where danger will not result or the flames must be smothered. In case of a small blaze, the fire may be extinguished with a cloth, preferably of wool, or if circumstances will permit, with ashes sand or earth. Alcohol dissolves in water and may, therefore, be diluted to a point where it will no longer burn. ACETYLENE-GAS MACHINES Acetylene is a gas that is generated when water is absorbed by calcium carbide, after the manner in which carbonic acid gas is evolved when lime slakes with water, but with the liberation of a larger amount of the combustible gas. Calcium carbide is a product resulting from the union of lime and coke, fused in an electric furnace to form a grayish-brown mass. It is brittle and more or less crystalline in structure and looks much like stone. It will not burn except when heated with oxygen. A cubic foot of the crushed calcium carbide weighs 160 pounds. Calcium carbide--or carbide as it is ordinarily termed--may be preserved for any length of time if kept sealed from the air, but the ordinary moisture of the atmosphere gradually slakes it and after exposure for a considerable time it changes into slaked lime. The carbide itself has no odor, but in the air it is always attended by the penetrating odor of acetylene, because of the gas liberated by the moisture absorbed from the air. If protected from moisture, calcium carbide cannot take fire, being like lime in this respect; it is therefore a safe substance to store. It is transported under the same classification as hardware, and will keep indefinitely if properly sealed.