Chromium trioxide (CrO₃), the hexavalent form, classifies under 281910. Chromium(III) oxide (Cr₂O₃) and other trivalent chromium oxides and hydroxides fall under 281990. The valence state is the critical distinguishing factor, and it also determines the applicable regulatory and safety requirements.

Antidumping or countervailing duty orders can apply to specific chromium compounds from particular origins. Importers should check the current USITC and CBP ADD/CVD order lists by tariff line and country of origin, as the scope of any order is defined precisely and may not cover all subheadings equally.