Unfortunately there is no safe distance. Fleas are notorious at being athletic jumpers and move around freely from one spot to another. In addition, fleas like to live in the environment, especially soft furnishings — where they lay eggs which will hatch into the next generation. The best way to protect your bedding and clothes is to spray an effective environmental spray which kills larvae and has a persistent action for seven – 12 months. Your vet can suggest an appropriate product.