Dry as a Bone To prevent mildew smell, thoroughly dry towels and sheets. If you prefer to line dry your linens, give them a quick pop in the dryer before storing them away to ensure they're completely dry. The dryer also gives you a chance to put in a fabric-softener sheet for extra fragrance.
Why do my sheets always smell musty?
Bacteria and fungi are usually the source of musty odors and their favorite conditions are damp and still. ... So even though your sheets are perfectly dry when they are placed on the shelf, they absorb the humidity in the air providing a great environment for bacteria and mildew.