When you store a backpack for a long period of time, or when the backpack is stored in a high moisture area, a mildew smell often develops. It is important to get rid of the mildew in order to keep the backpack in usable condition, as items that you place inside of the bag will also absorb the unpleasant odour. Remove the odour with ease using some common household products.
Open all compartments of the backpack, and sprinkle a heavy dusting of baking soda into all openings.
Close all compartments and let the baking soda sit in the backpack overnight.
Shake out the backpack outdoors the following day to get rid of the baking soda.
Fill the sink with 1 tsp washing powder and 1 gallon warm water. Agitate the water to create suds.
Dip a rag in the soapy water, squeeze out excess water, and wipe over the entire backpack. Keep all of the compartments open and allow the bag to air dry. Repeat if needed until all mildew odour is removed.
Place the damp backpack in front of a fan or outside to speed drying and prevent mildew from forming.