Mouldy tea typically shows visible fungal growth (white, green, or black fuzz), has a distinctly off-putting musty or chemical smell beyond the normal 'aged warehouse' notes of intentionally stored teas. If in doubt, discard. Prevention is straightforward: store tea below 65% relative humidity in a sealed container, away from strong odours and light. Never store tea in a humid bathroom or kitchen. Puerh and dark teas stored at 70-80% humidity for deliberate ageing are different — this is intentional and controlled.
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