Silk flowers that have not been stored in a cool dry place may take on mold and fungus spores that cause an unpleasant musty smell. You won't see anything because the spores are microscopic, but you will notice the smell when you start to place them in a silk flower arrangement. Dusting the flowers only sends the spores into the air and makes them smell worse. Spraying them with an air freshener only covers the smell temporarily. To get the musty smell out of silk flowers you need to kill the mold and fungus that is causing it.
Set your silk flowers on a clean, dry work surface covered with paper that has no writing on it. Old paper grocery bags work well when you place the printed side down.
Prepare an anti-mold and fungus spray by pouring 1 cup water, 1/2 cup white vinegar, and 1 tbsp. of lemon juice into a clean, dry spray bottle. Screw the top on securely and shake it to mix the ingredients.
Spray the vinegar spray liberally on the silk flowers. Be sure to spray between the petals where mold and fungus like to hide. The acidic properties of the vinegar and lemon juice will kill the mold and fungus spores. Allow the flowers to dry naturally.
If any musty smell remains, spray the silk flowers a second time.