The only 100 percent waterproof dust and will not clump or absorb moisture in wet areas. It is approved for use in commercial food handling establishments, making it an ideal tool for eliminating pests in wet areas of these accounts. DeltaDust is also labeled for application directly into drains that lead to sewers, a common place to find cockroaches, phorid flies and other pests. Kills crawling insects for up to 8 months when left undisturbed. For use indoors and outdoors. Does not clump or absorb moisture. Non-staining and odorless. Controls numerous stored-products pests.