Classification under 3824 is residual—it applies only when the preparation does not meet the terms of a more specific heading. Work through the chapter notes and the relevant heading texts in order; if the product's principal constituent or function is described elsewhere (e.g., adhesives under 3506, surface-active preparations under 3402), that heading takes priority over 3824.

Mixtures containing substances listed under the Stockholm Convention—such as PCBs (382482), DDT and related POPs (382484), and PFOS (382487)—may be subject to EPA import restrictions and reporting requirements under TSCA, in addition to any applicable trade-remedy measures. Importers should verify current EPA and CBP guidance before shipment.

Many tariff lines under 3824 originating from China are subject to Section 301 measures. Because the measure attaches at the specific 10-digit HTS line and country of origin, importers should check the applicable line rather than the heading as a whole.