The function of a hair drier is not only to dry your hair faster, but also to allow you to style your hair as it dries. Hair, when washed would dry naturally too but it would take longer. To speed up this process, a hair drier uses a fan to blow air over the hair. The movement of air helps to take away the moisture from the hair, thus speeding up the drying process.
To further quicken the drying of the hair, a heater is used. When the fan of the hair drier blows air across the heater, warm air is moved across the wet hair and dries it faster.
In addition to the heater and the fan, common hair driers have a switch to control the speed of the fan. A few hair driers even have a switch to control the temperature of the heater. These switches help to control the speed at which the hair dries.
The heater is made of nichrome, which is an alloy of nickel and chromium. Nichrome offers high resistance to the flow of electricity. Its high resistivity causes nichrome to heat up faster when an electrical current is passed through it. Also, nichrome does not easily oxidise when heated up. Other metals like iron rust easily when heated.
It has been found that temperatures above 600C can harm the scalp and the hair itself. A good hair drier therefore will have a thermal cut-off, which is usually in the form of a bi-metallic switch. When the temperature rises too high, the bi-metallic strip bends and breaks an electrical contact. This switches off the power to the heater.
The function of the safety grill over the air inlet is to prevent external objects like strands of hair, from being sucked into the fan.
As the inside of the hair dryer is at a high temperature, the hair drier nozzle as well as the entire body is properly insulated to make it safe for the person using it.