HOT BLAST. The apparently insignificant idea, introduced by Neilson in 1828, of sending hot air instead of cold into a blast furnace created a revolution in smelting practice, for it enabled a much greater quantity of ore to be smelted for a given amount of fuel, while furnaces could be made of larger size than hitherto. The air temperature employed was at first low, but now ranges from about 650° F to 1,500° F. Hot blast stoves for the heating were originally fired with coal, but now the waste gases from the furnaces are utilized by means of combustion chambers in the stoves. These are of regenerative type, tall structures con taining a mass of brick checker-work.
Stoves vary considerably in regard to the interior arrangement.
(See IRON AND STEEL.)