Ethane is a saturated acyclic hydrocarbon and classifies under subheading 290110 along with other saturated compounds such as butane and pentane. Ethylene (ethene) is unsaturated and has its own dedicated subheading, 290121. The saturated/unsaturated distinction is the primary classification dividing line within the heading.

Section 301 measures apply at the 10-digit tariff-line level based on country of origin. Some lines covering specific unsaturated hydrocarbons sourced from China carry Section 301 exposure. Importers should verify the current Section 301 annex for the specific tariff line and origin before entry, as coverage and rates can change.