Abstract: A building for the manufacture of integrated circuits which includes a manufacturing equipment floor with processing equipment for the manufacture of integrated circuits, a floor under the manufacturing floor has supporting equipment associated with each of the processing equipment, and an upper floor above the manufacturing floow supports a plenum system that provides at least two classes of clean air circulation to the manufacturing floor. Each piece of processing equipment is enclosed with means to separate it from the surrounding air. A clean air input of the highest class of clean air purity is provided to the processing equipment in the enclosure. The air/gas exhaust is directed through an air/gas handling system. Means are also provided to provide the surrounding areas a clean air input of a lower class of clean air purity from the plenum system and the air/gas exhaust directed to an air/gas handling system.