A residual catch-all for inorganic chemical substances that do not fit more specific headings, this category spans distilled and conductivity water, liquid air (with or without rare gases), compressed air, and miscellaneous amalgams. Conductivity water and ultra-pure distilled water are critical inputs for semiconductor wet-bench processes and pharmaceutical manufacturing, while liquid air is traded as an industrial gas for cryogenic applications. Because the heading is defined by exclusion, correct classification requires ruling out all more-specific inorganic compound headings before applying it. The breadth of the category means duty rates and any applicable trade-remedy exposure vary significantly by the specific substance.

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