Almost all options we found either only use hot air for their designs, or they sport a function to allow users to turn it off. Customers often wonder if putting their leather or plastic gear on these designs is going to hurt or damage the material. We found that very few designs out there are able to achieve temperatures hot enough to do any real damage to your gear. However, if you are worried about this, you can always opt for a design that allows users to turn off the heat setting. Keep in mind, however, that if you turn off the heat, it is going to take significantly longer to work properly, and you aren’t going to be able to experience that wonderful feeling of slipping your foot into a pair of nice and toasty shoes!