In a building with electricity it is normal for safety reasons to connect all metal objects such as pipes together to the mains earth to form an equipotential zone. This is done in the UK because many buildings are supplied with a TN−C−S earthing system where the neutral and earth conductors are combined. Close to the electricity meter this conductor is divided into two, the earth and the neutral busbar in the consumer unit. If the ground connection to the neutral is lost, all wiring and other objects tied to the neutral will be energized at the line voltage. Examples of articles that may be bonded include metallic water piping systems, gas piping, ducts for central heating and air conditioning systems, and exposed metal parts of buildings such as hand rails, stairs, ladders, platforms and floors.