When a musty smell is present in your dryer, it is usually a sign that you have mildew somewhere in your dryer. This may come as a result of forgetting wet clothing in the dryer with the door closed or from repeated exposure to mildewy fabric, such as smelly towels. Regardless of the reason, it's important to remove the smell so neither it or the mildew transfers to your clean laundry. Regular cleaning and care with simple products from home can keep your dryer smelling clean.
Wear rubber gloves to keep your skin from getting dried out by the bleach solution you make for cleaning the mildew smell out of the dryer. Mix 1/2 cup bleach with 1 gallon warm water in a bucket and swish around to blend the two ingredients.
Wipe down the inside of your dryer with a clean cloth and the bleach solution. Clean the inside of the dryer door, as well, then leave the door open so the inside can air-dry.
Pour undiluted white vinegar into a spray bottle. Lay a few old towels flat on a work surface. Spray the towels with the vinegar so they are wet but not dripping.
Place the vinegar-sprayed towels into your dryer and dry them. As the towels tumble around in the dryer the vinegar kills any remaining mildew and rids your dryer of the mildew smell.
Remove the dried towels and leave your dryer door propped open to air it out.