the gases rise up and are collected on the top of the furnace. as the gas contains a lot of carbon monoxide, it is a valuable fuel. the gas collected on the top of the blast furnace is called "blast furnace gas". it is then washed and dried and all solid particles such as soot or ore dust are collected. the gas is then burned in special ovens called "cowper stoves" or "hot blast stoves" into carbon dioxide. the heat from burning the blast furnace gas is then used to pre-heat the blasting air, "wind", which in turn is blasted into the blast furnace itself.