Blocked Venting on a Dryer

This is what the inside of a dryer with blocked venting looks like. Mounds (inches thick sometimes) of lint. A real potential fire hazard. At least twice a year you should check the air flow at your outside wall cap.  Also make sure that there is not a lint buildup. This is especially true if you have a mesh cage over the wall cap to prevent animals from getting in. Those meshes are notorious for catching and building lint.