The practice of preheating the air forced into a blast furnace in order to improve the efficiency of working of the furnace; the blast of hot air so used.
Origin
Mid 19th century. From hot + blast.
Definition of hot blast in US English:
hot blast
noun
The practice of preheating the air forced into a blast furnace in order to improve the efficiency of working of the furnace; the blast of hot air so used.