Hair dryers speed the drying process of hair by blowing air, which is usually heated, over the wet hair shaft to accelerate the rate of water evaporation.
Excessive heat may increase the rate of shaft-splitting or other damage to the hair. Hair dryer diffusers can be used to widen the stream of air flow so it is weaker but covers a larger area of the hair.
Hair dryers can also be used as a tool to sculpt the hair to a very slight degree. Proper technique involves aiming the dryer such that the air does not blow onto the face or scalp, which can cause burns.
Other common hair drying techniques include towel drying and air drying.