Stoves used to heat air to very high temperatures before delivering it to the main furnaces.
 
 

Stove Room III

The Stove Room consisted of many of these smaller 'furnaces' in which air was heated to a high temperature and passed on to the main furnace where iron production occurred. The stoves themselves are now covered with graffiti. Nonetheless, the stoves and their interconnecting network of pipes make an incredible array of interesting lines and shapes.

The audio segment for this photo describes how the stoves were used.