Baker's yeast, which is live and active at the time of export, classifies under 210210 (active yeasts). Nutritional yeast is deliberately deactivated and classifies under 210220 (inactive yeasts and other dead single-cell microorganisms). The key criterion is whether the yeast retains leavening activity; a certificate of analysis confirming inactivation supports the 210220 classification.

Only dead single-cell microorganisms that are not medicinal vaccines fall under 210220. If a dead microorganism product is formulated as a pharmaceutical or vaccine, it moves to the pharmaceutical heading. Probiotic preparations containing live cultures are generally classified elsewhere based on their formulation and intended use. A binding ruling from CBP is advisable for borderline probiotic products.