What Are Those Little Boxes on Hair Dryer Cords?

Ground fault circuit interrupters should be installed in areas where water and electricity are in close proximity.

In the early 1980s, deaths caused by hair dryers falling into bathtups or sinks with water resulted in about 18 deaths per year. 

Since 1991, hair dryer manufacturers have been required to include ground fault circuit interrupters on hair dryer cords. GFCI outlets can sense unsafe electrical hazards and they automatically shut off power before a serious injury or electrocution can occur. 

Since then, the number of hair dryer deaths has dropped to about two per year.

Source: e-SMART