Bad Odor Blocks are odor counteractant wafers that attract and remove bad odors. Most effective in small rooms, ducts, automobiles or wherever odor control is needed. Long-lasting odor control. Use this simple, set-and-forget wicking block to quickly suppress odors in virtually any location. Available in multiple scents, this natural block can provide odor control for months depending on application. Each block holds more than three times its weight in active ingredients.