The duvet itself deserves an hour
Whatever duvet you're bringing out, give it a day of air before it goes on the bed: draped over a banister, a clothes horse or a line on a dry, breezy day, turned once halfway through. Shake it out from the corners to redistribute the filling, and if it's spent the summer compressed, a tumble on a no-heat or cool air cycle with a couple of clean dryer balls will bring the loft back faster than anything else. Washing a duvet is a bigger undertaking and depends entirely on the filling and your machine's capacity, so read the label before you commit — an under-rinsed or under-dried duvet is exactly how you create a much worse smell than the one you started with.
Do I really need to wash bedding that was clean when I put it away?
Yes, and it takes one cycle. Stored fabric picks up the character of the space it sat in and holds dust that settles even through a closed cupboard door, so a wash and a thorough dry is what turns "technically clean" into "smells like a hotel". If the set has been in storage for more than a season, wash it the day before you plan to use it rather than the morning of, so nothing goes on the bed even slightly damp.
How do I get a musty smell out of a duvet I can't wash?
Air it outdoors on a dry, breezy day for several hours, turning it once, which handles most mild staleness on its own. If the smell lingers, a cool-air tumble with dryer balls helps, and a fresh, freshly washed cover adds the final layer — but if a duvet smells genuinely damp rather than stale, or if there's any visible discolouration, it's worth replacing rather than rescuing.
