Thunerstorms are the primary source of lightning. Because people have been struck many miles away from a storm, seeking immediate and effective shelter when thunderstorms approach is an important part of lightning safety. Contrary to popular notion, there is no 'safe' location outdoors. People have been struck in sheds and makeshift shelters. A better alternative is to seek shelter within an enclosure of conductive material (such as an automobile which is an example of a crude type of Faraday Cage). Once inside the enclosure, it is advisable to keep away from any attached metallic components (such as keys in an ignition, etc...). If thunder can be heard, there is a risk of being struck.