Moth balls can be somewhat useful in preventing infestations.
Mothballs are designed to be used in closed containers to eliminate moths by suffocating the moths in the fumes within the container.
The problem is that area rugs can’t be stored in air right containers, as they will begin to rot over time.
They are not meant to be used in a storage facility (and especially not in your home) to prevent moths from reaching your rugs when they’re rolled up as a fool-proof way of preventing infestation.
If you’ve ever paid the price of forgetting to spray just one area of your body with mosquito repellent spray, you’ll know that you’ll need a thorough inch-to-inch coverage here too; otherwise, the moths will gather up in a safe zone where moth balls aren’t present.
Taking your rugs out of storage and inspecting/vacuuming them every three to six months is the best way to assure your rugs are safe in storage.
There are products such as MasterBlend’s moth repellant that can be applied by professional rug service providers which may prevent new moth infestations from happening in your rug.
We haven’t personally tested these products, but from what we’ve heard from three different reputable rug experts who have used the product, they are effective.