Domestic gas meter connected to a gas pipe (lower left). The meter is in a box fixed to the external wall of a house. It measures the volume of gas passing from the gas pipe to the appliances inside the house. Natural gas is a fossil fuel used in appliances like central heating units, kitchen stoves, and domestic boilers. This meter is the U6 model from Actaris, designed for use in the UK. It has a capacity to channel 6 cubic metres of gas per hour. Photographed in the UK in 2006.