The device enables the safe burning of a continuous stream of gas without the risk that the flame will travel back down the tube connecting the burner to the gas supply. In modern usage it is most common for the burner to run on natural gas, a combination of propane and butane. Natural gas is prinicipally methane with only small amounts of propane and butane.
The burner has a weighted base, into which the gas supply tube plugs, and a tube rising vertically from this base. Around the bottom of the tube, there is a metal collar, which may be turned to reveal more or less of a hole made in the side of the tube.
The gas flows from the connection to the gas supply, through a small hole at the joint between the base and the tube. This stream of gas then passes the hole in the side of the tube, mixing with air if the hole is open. At the top of the tube, the gas is ignited, and burns.
If the collar at the bottom of the tube is adjusted such that more air can mix with the gas before combustion, then the flame will burn hotter (appearing blue). However, if the hole is closed, the gas must mix with oxygen in the atmosphere at the point of combustion, and thus burns less efficiently, producing a cooler flame (appearing yellow). By adjusting this, and the in-flow of gas, then the heat of the flame can be controlled.