Like many fabrics, denim may pick up a bad odor. Rubber, especially when new, has a very strong and distinctive chemical odor. If you work with, or otherwise handle rubber products, such as tires, for example, this strong odor may permeate and linger in denim. Scented detergents may work in some cases, but often they only mask odor. A couple of common household products can neutralize this odor, rather than temporarily masking it.
Place the denim items in your kitchen sink or your washing machine. Fill either with warm water.
Add ½ cup of baking soda. Stir the water with your hand to help the baking soda dissolve in the water.
Let the denim item soak for ½ an hour. Place the item in a washing machine with your regular detergent and run it through a wash cycle, stopping it when it gets to the rinse cycle.
Pour 1 cup of white vinegar into the machine and run the denim through the rest of the cycle.
Remove the denim article from the washing machine and hang it in an airy place, preferably outdoors, to dry. If the rubber smell lingers after the item has dried, simply repeat the whole process--but leave the item to soak in the baking soda for a longer period of time--up to an hour.