Hair dryers are usually used to speed up drying wet hair. The main parts of a hair dryer are a motor-powered fan and an electrically heated element. The element heats up when an electric current flows through it. When air from the fan goes through the barrel of the hair dryer, it is heated by the element. Straightening irons, straighteners, or flat irons work by breaking down the positive hydrogen bonds found in the hair's cortex, which cause hair to open, bend and become curly.