Kaupunkikaasu

Kaupunkikaasu, also known as town gas or coal gas, is a flammable fuel gas that was historically produced from the destructive distillation of coal. This process, known as coal carbonization, involved heating coal in the absence of air to produce coke, coal tar, and town gas. The gas produced was primarily composed of hydrogen, methane, and carbon monoxide, with smaller amounts of other hydrocarbons and inert gases.

For much of the 19th and early 20th centuries, town gas was a primary energy source for lighting, heating, and cooking in urban areas. Gasworks were established in cities to produce and distribute the gas through a network of underground pipes. The introduction of electric lighting gradually reduced the demand for gas for illumination, but it remained important for heating and cooking for many decades.

The composition of town gas varied depending on the coal used and the production method, but the presence of carbon monoxide made it toxic if inhaled in significant quantities. As natural gas, which is primarily methane, became more widely available and cheaper to extract and transport, town gas production declined. Natural gas is a cleaner-burning fuel and does not contain the same levels of toxic byproducts as town gas. Most remaining town gas systems were converted to natural gas or discontinued altogether.