Static shocks and how to avoid them: "Why do I get shocks when I touch the door knob or filing cabinet?
Most modern shoes have highly insulating rubber or plastic soles. As you walk, static charges can build up on the soles of the shoes. This is especially true if the floor is also insulating. Some older nylon carpets are particularly good at generating static electricity.
The charge on the shoes soles induces static electrical charge on your body, and this charge appears as a high voltage. Under severe conditions, more than 15,000 Volts have been recorded. It is quite common to experience 5,000V. In fact, many people do not feel a shock from a static electricity discharge less than about 2,000-4,000V.
If you are indoors, the point can be proved by walking around for a while with no shoes on - you will probably not experience shock."