Diagram shows the working of a pneumatic gas switch. When the knob on the wall is pulled out, air is drawn down the tube, and sucked inward to a piston at the other end. This piston draws over to the right a small lever, which turns on the gas to be ignited by the bypass. Pressing in the knob forces back the air, the piston and the lever to their original position, shown in the dotted lines, thus cutting off the gas. Gas lighting is production of artificial light from combustion of a gaseous fuel, such as hydrogen, methane, carbon monoxide, propane, butane, acetylene, ethylene, or natural gas. The use of natural gas for indoor lighting is nearly extinct. Besides producing a lot of heat, the combustion of methane tends to release significant amounts of carbon monoxide, a colorless and odorless gas which is more readily absorbed by the blood than oxygen, and can be deadly. Pneumatics is a branch of engineering that makes use of gas or pressurized air. No artist credited.