I just wanna add if your heating pad has settings such as hi med low or 1-5 or 1-3 or some such I wouldn't go over medium because heating pads get hot enough to burn past medium- just a thought. Air space would be good - just use those little feet from walmart (I got the thickest I could find)... It would probably be best if you could find a piece of plywood or something to put underneath.. I don't know how flammable carpet is or anything though so others may know more.