I've made and sold hundreds of these bags ( Nancy's Crafts in Nebraska ) and only if your microwave is extreme voltage OR you use poly filling rather than all natural, is it a fire hazard. You have to use 100% cotton throughout. Naturally you have to keep it soil free on the outside as well as inside and the potatoes need to be damp as well as the paper towels. Can't let them dry out. They work great! I've used one for 4 years now and no problem.