Extension Cord Safety-Take No Chances! We use extension cords almost every day both at work and at home. These are very useful devices, but they can present a fire or shock hazard when either worn out or used improperly. Types of extension cords Extension cords come in either two or three-wire types. Two-wire extension cords should only be used to operate one or two small appliances. Three-wire cords are used for outdoor appliances and electric power tools. The third wire on this cord is a ground and this type of cord should never be plugged into any ungrounded electrical outlet. Only grounded extension...