Abstract: A flask is filled with a heat resistant filling material, such as sand, to embed therein a pattern of the type which melts down and generates combustible gas when it is heated, a runner connected to the pattern and provided with a sprue and a hollow venting device having an open upper end and a sidewall provided with at least one vent opening. A molten metal is poured into the sprue. The molten metal reaching the pattern through the runner heats the pattern and causes it to melt down and generate gas. The molten metal occupies a cavity formed by the meltdown of the pattern and drives out the gas into the venting device through the filling material and the vent opening. The gas is burned at the upper end of the venting device. Disclosed also is an apparatus which can be used for carrying out the method as hereinabove summarized. The apparatus is useful for either a batch or a continuous type of casting operation.