Hair dryers are devices that blow air over wet hair for the purpose of drying it. They also allow you to control the shape of the dry hair by adjusting the speed and temperature of the air. Hair dryers require a number of safety features because they use electricity and are used in close proximity to water.
General Features
A hair dryer has a fan and a heating element. A basic model may have just an on/off switch and a switch to control air flow. Some basic models control these two functions with a single switch. A more advanced model of hair dryer also may have a control for the air temperature. Hotter air offers a better ability to shape the hair by drying hair more quickly than cold air does.
Fan
The fan in a hair dryer contains an electric motor that uses electricity to rotate very quickly. A turbine is attached to the motor and draws in air through inlets with its blades. The turbine then pushes the air down the barrel of the hair dryer to create the air flow.
Heating Element
The heating element in a hair dryer is typically a coil of Nichrome wire wrapped around an insulator. Nichrome is an alloy of the metals nickel, chromium and iron. It's used in heating elements because it is a poor conductor of electricity, meaning that a large portion of the electrical current in the wire is converted into heat. Nichrome also has the advantage of not oxidizing when it's heated, meaning it won't rust and subsequently break.
Ground Fault Circuit Interrupter
A ground fault circuit interrupter (GFCI) uses a polarized plug that can be plugged in only one way. It monitors the flow of electricity between the two prongs of the plug. The GFCI turns off the hair dryer by breaking the circuit if it senses a current leakage. All hair dryers in the United States have been required to have a GFCI since 1991.
Additional Safety Features
Hair dryers generally have a sensor that turns the hair dryer off if the air coming from the barrel rises above 140 degrees Fahrenheit. Many hair dryers also have a thermal fuse that turns the hair dryer off if the heating element gets too hot.
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