Extraneous rust

Workmanship. The standard of workmanship shall be such as to insure the Droduction of material meeting the requirements of this specification. The DPhA shall be free of extraneous material (such as iron rust, wood particles, dirt, colored salts and other visible impurities). The color of DPhA shall be no... 

In terms of facilities, the key issue was the common factory environment. It was the practice of isolating the final API in essentially the same environment as all prior intermediates. This potentially exposed the final API product to the same factory environment, where extraneous contamination ranging from paint chips from equipment to rust from overhead piping and unfiltered solids from earlier process steps could carry forward into the final product. 

It would be possible to consider extraneous effects as the cause. For example, iron would not rust if oxygen were kept from it. However, this is not the point, because substances that are separated from the environment also change. For example, these objects age by themselves ... 

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